Serial Communications Protocol Specifications - Swissvacuum.com

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ANGELANTONI Industrie S.P.A. 

Serial Communications Protocol 

Specifications 

For microPLC Chamber Controller 

Vers. 2.02 rev. B - September 1999 

REVISION REVISIONED CHAPTERS DATE AUTOR/S Q C. APPROVAL.(date and signature) 

A Emissione 22/09/98 Thecnical 

Office/pm 

11/02/98 

B 27/09/99 Software Dept. 27/09/99 

Serial communications protocol vers. 2.02 Angelantoni Industrie Spa Massa Martana (PG) Italy

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INDEX 

INTRODUCTION...............................................................................................................................................................................4 

ERROR DETECTION.......................................................................................................................................................................5 

COMMUNICATION ERRORS .........................................................................................................................................................6 

IDENTIFICATION OF A DATA PACKET.........................................................................................................................................7 

MODBUS FUNCTIONS....................................................................................................................................................................8 

FIELDS DESCRIPTION ...................................................................................................................................................................9 

MODBUS FUNCTIONS DESCRIPTION .................................................................................................................................... 10 

READ MULTIPLE REGISTERS: FUNCTION CODE: 3 (DECIMALE)....................................................................... 11 

WRITING FUNCTION: FUNCTION CODE: 16 (DECIMAL) ......................................................................................... 12 

COMMUNICATION PARAMETERS............................................................................................................................................. 13 

CODE EXAMPLES......................................................................................................................................................................... 14 

C LANGUAGE .......................................................................................................................................................................... 15 

VISUAL BASIC.......................................................................................................................................................................... 17 

EXAMPLES OF READING AND WRITING QUERY.................................................................................................................. 18 

CALCULATED CRC TABLES...................................................................................................................................................... 24 

mICROPLC MEMORY LAYOUT VERS. 2.0 ............................................................................................................................... 25 

READING AREA............................................................................................................................................................................. 26 

PT100 MEASURES................................................................................................................................................................. 26 

ANALOGIC INPUTS MEASURES ......................................................................................................................................... 26 

CALCULATED INPUTS MEASURES................................................................................................................................... 26 

MESSAGES .............................................................................................................................................................................. 28 

USER AND REAL SETTINGS ............................................................................................................................................... 29 

SETPOINTS READING........................................................................................................................................................... 32 

TEST PROGRAM STATUS..................................................................................................................................................... 33 

WRITING AREA.............................................................................................................................................................................. 34 

NOTE ............................................................................................................................................................................................... 36 

APPENDIX A: CONNECTION OF A SERIAL CABLE ......................................................................................................... 37 

Figures 

Fig. 1 Master and Slave Pag. 3 

Fig. 2: Communication overview Pag. 4 

Fig. 3: Noise on the line Pag. 4 

Fig. 4: Decoding a data packet Pag. 5 

Fig. 5: Frame identification Pag. 7 

Fig. 6 CRC calculation Pag. 12 

Fig. 7: System logic layout Pag. 23 

Fig. 8: Serial cable Pag. 32 


INTRODUCTION 

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The present document contains information on the Modbus protocol for performing data exchange between a PC and 

the MicroPLC chamber controller. You can find here a short description of the query and answer sintax for the 

Modbus function 3 (read function) and function 16 (write function). 

Moreover, a short example of code has been included as a guideline for the development of a complete program. 

A communication protocol defines media, data formats and rules which are common to two or more systems wich 

must exchange informations by means of a phisical communication line. 

Moreover is described here how the devices (master and salve) connected to the line interact between them to start 

and close the communication, and the way to identify error conditons during the data transmission. 

Pratically the protocol allows a data exchange between Master device and a Slave device according to the following 

situation: 

Fig. 1 Master and Slave 

PC as MASTER CHAMBER CONTROLLER as SLAVE 

SLAVE ADDRESS 

FUNCTION CODE 

DATA 

ERROR CHECK 

SLAVE ADDRESS 

FUNCTION CODE 

DATA 

ERROR CHECK 

In this architecture, PC always acts as Master while the chamber controller is always the Slave device. 

The Master device is the only one that can start the communication. 

The communication consists essentially in a query made by the Master device (normally a PC) that is directly 

followed by an answer coming from the Slave device (the MicroPLC chamber controller). 

The communication task, either is a query or an answer, consists in preparing a data packet wich includes the 

identification code of the requested function, the lenght of the query/answer, the data itself and error check 

information. This data packet is then transmitted to the device on the other end of the serial communication line. 

Thus the Modbus protocol defines the structure of the data packet in wich the relevant information to be exchanged 

are encapsulated. The fields consituting the data packet are: destination address, function code of the action to be 

performed, the relevant data for the operation and an error verification code. 

When a Slave device receives a data packet, it decodes the data and execute the operation that the Master device 

has required (operation that can be reading or writing data in the Slave device memory). 

At this point the Slave device create the needed data packet and “returns it to sender”. The information in the 

response message is the slave device address, the action performed, the data acquired as a result of the action and a 

mean of checking errors. 


The entire task can be described as follows: 

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Fig. 2 Communication overview 

MASTER (PC) SLAVE (CHAMBER CONTROLLER) 

Prepare query to send 

Send query to the slave via serial line. 

Wait answer from the Slave 

The Modbus protocol implemented in the MicroPLC chamber controller is the binary type (also known as RTU). In 

RTU mode data are sent as 8 bits binaries characters. A remote control computer (typically a PC) is always the 

master device meanwhile the MicroPLC controller is the slave device. 

ERROR DETECTION 

As well known, communication errors can occour during data transmission on a serial line. The errors generally come 

from noise on the line and electrical or hardware problems on the devices used for the communication. 

The software that controls the communication (the PC) takes care to identify the errors and manage them with 

appropriate actions. 

Specifically, when an error is detected, the data packet must be discarded (not used) because the data inside are 

probably corrupted and meaningless. 

Only when no error is present, the data packet can be decoded to extract the answer coming from the chamber 

controller. 

The errors can be present in both sides of the serial line (PC side and chamber controller side). If the error is identified 

by the chamber controller, then no answer will be send to the master. 

Fig. 3 Noise on the line 

Wait data from the master 

Decode packet and prepare the 

answer 

Send packet to the master 


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Fig. 4 Decoding a data packet 

There are 2 types of errors which may occour: transmission errors and programming or operation errors. The Modbus 

system has specific methods for dealing with either type of error. 

COMMUNICATION ERRORS 

This kind of errors happens when a condition of FRAME or PARITY or OVERRUN error is detected (generally due to 

same problems of noise on the transmission lines) or when an invalid CRC (cyclical redundancy check) is found in the 

received data packet. 

When one or more of these errors is detected, the message (probably damaged) is not processed: the Slave 

device (microPLC) will not answer to the message. 

Operation / programming errors 

Are those which present incorrect data in a message. In this case the Slave device (MicroPLC) produces an 

“exception” depending on the error type; the exception error code is inserted in the answer data packet, so that it 

allows the master device (PC) to identify the error condition. 

To identify this exception, the most significant bit of the function code of the answer packet (coming from the 

microPLC to the PC) is set to 1. 

Exception codes 

Serial communication line 

MASTER SLAVE 

Data packet 

Any error ? 

No 

Decode the packet to get the 

answer from the slave. 

Noise 

Ye 

01 Illegal function 

02 Illegal data address 

Do not use the packet 

because corrupted 


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03 Illegal data value 

04 Failure in associated device 

05 Acknowledge: the slave is processing the request 

06 Busy: busy device, rejected message 

NAK: It is impossible to execute the requested function 

07 Memory parity error 

For example, let us say that we want to read data from the slave. Master prepares a data packet (query) with modbus 

function code 3 (function code 3 identifies a READ request as we will see later) and send the packet to the slave. 

In preparing the answer, the slave will return the same function code if no exception is present, otherwise it will return 

the exception code as reported below (note that only the first two bytes of the data packet are showed here: the 

detailed explanation of the entire frame will follow in the specific paragraph) 

0 ADDRESS Chamber controller address 

1 03 dec: 00000011 binary Modbus function code for read operation 

2 …. 

3 …. 

4 …. 


1 03 hex: 00000011 binary Modbus function code for read operation 

2 …. 

3 …. 

4 …. 


1 83 hex: 10000011 binary Modbus function code + exception 

2 02 Exception number: illegal data address 

3 Error check 

4 Error check 

IDENTIFICATION OF A DATA PACKET 

Two different ways are available to the programmer to identify a data packet in binary mode: 

� FRAME SYNCHRONIZATION 

� LENGHT SYNCHRONIZATION. 

In the following section a short description of both will be done in order to have an overview on advantages and 

difficulties of both. 

FRAME SYNCHRONIZATION 

QUERY FROM THE MASTER TO THE SLAVE 

ANSWER FROM THE SLAVE, NO EXCEPTION 

ANSWER FROM THE SLAVE, EXCEPTION 02 

Frame synchronization can be manteined in binary transmission mode (RTU) only by simulating a 

synchronous message. The receiving device monitors the elapsed time between receipt of characters. 

Modbus specifications requests that this time (time between the reception of a character and the following) is 

less or equal to 3.5 times the time of character transmission because the received data can be considered 


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as part of the current data packet. If not, the character will be considered as the first character of a new data 

packet. 

For example, at 9600 bps the time between the transmission of a character and the next one is approximately 

800 microsec. If the next character will be received after more than 800 * 3.5 microseconds, 

the character will be the first of a new data packet. 

The following picture shows how a received character belongs to the current data packet (frame) or begins a 

new frame according to the time elapsed since the previous character was detected. 

In this picture the horizontal axis is the time axis and each rectangle identifies a character. A packet consists 

of all characters with intercharacter time less than time specified by Modbus (T = 800 * 3.5 microseconds at 

9600 bps) 

More than 

T=2800 microsec. 

Fig. 5 Frame identification 

Note that this method requires a very precise timing to get data from serial line. Considering that Windows is not a real-time 

system (and so it cannot garantee the timing required) it is preferable not to use it under this operating system. 

LENGHT SYNCHRONIZATION 

Each modbus function has a well defined length, both for queries and answers. Knowing these lengths, it is possible 

to identify the end of a packet while receiving. 

This way of operation is probably the simplest to use, both for development of a commincation software and for the 

debug operation. 

In effect you always know how many character you are waiting for according to the query you sent to the slave device. 

This is also true when an error occours during the communication: the lenght of an answer with an exception is 

however known. 

MODBUS FUNCTIONS 

Previous frame 

Data packet 

Time between characters is less 

than 800*3.5 microseconds: the 

characters belongs to the current 

New frame 

More than 

T=2800 microsec. 

All the operations with the chamber controller can be done with only two of the Modbus functions: 


� Read Function: function code 3 (decimal) 

� Write Function: function code 16 (decimal) 

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Master can use these functions in order to take actions on the slave (chamber controller). 

READ FUNCTION (FUNCTION CODE: 3) 

The Modbus read operation (function code 3) can be described as follows: 

FUNCTION 

QUERY LENGTH 

ANSWER LENGTH 

CODE 

( without error check field) ( without error check field) 

3 (decimal) 6 bytes 3 bytes + content of the 3 rd 

WRITE operation (FUNtION CODE: 16) 

The write operation (function code 16) is described as following 

FUNCTION 

QUERY LENGTH. 

CODE 

( without error check field ) 

16 (decimal) 7 + the content of the 7 th 

byte 

In order to get the total data length, add 2 bytes for CRC. 

byte of the answer 

LUNGHEZZA RISPOSTA 

( without error check field) 

6 bytes 

Each function is organized in fields with specific meaning. In the following section a short description of the fields is 

given, and a detailed explanation of the read and write functions follows. 

FIELDS DESCRIPTION 

ADDRESS FIELD 

This is the first field of the structure and consists of 1 byte. This byte identifies the address of the chamber 

controller (slave) to work with. 

Each slave must have a unique address and only the addressed slave will respond to a query that contains its 

address. 

The chamber controller address is always 17 (decimal) 

FUNCTION FIELD 

Tells the addressed slave what function to perform. The high order bit (High Order HO in the following) in this 

field is set by the slave device to indicate that other than a normal response is being transmitted to the Master 

device (see the discussion regarding the exceptions in the answer). The bit remains 0 if the message is a query 

or a normal response message. 

DATA FIELD 

Contains information needed by the slave to perform the specific function or it contains data collected by the 

slave in response to a query. 

ERROR CHECK FIELD 

The error check field uses a CRC calculation, which described later in the examples. 


MODBUS FUNCTIONS DESCRIPTION 

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For each function an example is given for the query packet from the PC and the answer packet from the slave. Take 

into account that the chamber controller has 17 (decimal) as address and that the addresses of the memory locations 

to read from and to write to are listed in the next section of this manual. 

Some conventions are used to describe the data inside the functions: 

“HO”: High Order or Most Significant (refers to bits or bytes depending on the situation) 

“LO”: Low Order or Least Significant (refers to bits or bytes depending on the situation) 

“Register”: a memory location inside the chamber controller memory area; it consistes of 2 bytes 

Master prepares a query packet to read from or to write to the chamber controller, then waits for the answer. When 

the answer is available a check is done to identify the errors (if any). The decode operation is the last action to be 

performed when no errors have been encountered in the data packet. 


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READ MULTIPLE REGISTERS: FUNCTION CODE: 3 (DECIMAL) 

Allows the user to obtain the binary contents of holding registers in the addressed slave (the chamber controller) 

The addressing allows up to 125 registers to be obtained at each request. 

The registers are numbered starting from 0. 

The below example reads 104 registers from slave starting at address 2000. All values are in decimal format. 

Note that the following table is exactly the content of a byte array you can send to the serial device in order to read 

from the chamber controller. 

QUERY 

INDEX MEANING TX BUFFER 

0 MPLC ADDRESS 17 

1 FUNCTION NUMBER 03 

2 DATA START REGISTER, HO 07 

3 DATA START REGISTER, LO 208 

4 REGISTERS TO BE READ, HO 00 

5 REGISTERS TO BE READ, LO 104 

6 ERROR CHECK 70 

7 ERROR CHECK 57 

ANSWER 

The addressed slave responds with its address and the function code, followed by the information field. The 

information field contains 2 bytes describing the quantity of data bytes to be returned. The contents of the 

requested registers (data) are two bytes each, with the binary content right justified within each pair of 

characters. 

The first byte includes the high order bits and the second the low order bits. 

DATA MEANING 

17 ADDRESS 

03 FUNCTION NUMBER 

208 (&HD0) BYTE IN THE PACKET (REG. REQUESTED * 2) 

HO OF REG. OF DATA OUTPUT 0 

LO OF REG. OF DATA OUTPUT 0 

HO OF REG. OF DATA OUTOPUT 1 


HO OF REG. OF DATA OUTPUT 2 


------ 

------ 

ERROR CHECK 

ERROR CHECK 

The total length of the data packet expected is of 213 bytes (3 bytes of header + 208 + 2 bytes CRC) 

Data that must be decoded 

according to the description of 

microPLC memory 


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WRITING FUNCTION: FUNCTION CODE: 16 (DECIMAL) 

NOTE: 

This operation overwrite existing memory values. Be carefull to write only to the right position 

according to the microPLC memory layout. 

Wrong write operation (wrong address) can damage specific memory contents reserved to the 

functionality of the system. 

Registers existings within the controller can have their contents changed by this message (a maximum of 60 

registers) 

The following example shows the writing of 30 registers (60 bytes) at address 2300 (decimal). This address is a 

controller memory area reserved to write operations for chamber control. You can find the description of this 

area in the specific section of this manual. 

All values are in decimal. 

QUERY 

Data that must 

be written in 

the controller 

memory 

ANSWER 

DATA MEANING 

17 ADDRESS 

16 FUNCITON NUMBER 

08 REG. ADDRESS HO 

252 REG. ADDRESS LO 

00 REG. NUMBER HI 

30 REG. NUMBER LO 

60 BYTES NUMBER 

------ DATA HO 

------ DATA LO 

DATA HO 

DATA LO 

ERROR CHECK 

ERROR CHECK 

The normal answer to function 16 returns the following data, with a total packet length of 8 bytes. 

DATA MEANING 

17 ADDRESS 

16 FUNCTION NUMBER 

08 ADDRESS HO 

252 ADDRESS LO 

00 REG. NUM. HO 

30 REG. NUM. LO 

128 ERROR CHECK 

193 ERROR CHECK 

Bytes number = 

2 * num. Of 

registers. 


COMMUNICATION PARAMETERS 

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The following parameters must be used to configure the serial port of the PC in order to communicate with the 

chamber controller. 

These parameters cannot be changed. 

NAME VALUE 

BAUD RATE 19200 

PARITY NONE 

STOP BITS 1 

DATA LENGHT 8 


CODE EXAMPLES 

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In this section we show how to compute the CRC according to the Modbus protocol requirements. Note that the CRC 

must be added to the packet to be sent to the controller and also must be computed on the received packet to verify 

its integrity. 

Also some little programs are reported on how to prepare a query packet to talk to the controller using C language 

and Visual Basic. 

QUERY 

ANSWER 

Prepare data packet 

CRC calculation 

Add CRC at the end of 

data packet 

Get the answer from the 

serial port buffer 

CRC calculation on the 

received packet 

Compare the computed 

CRC calcolato with the 

CRC in the data packet 

No match: data packet 

corrupted: do not use it! 

Fig. 6 – CRC calculation 

Send packet 

Receiving a data packet 

CRCs match: data packet 

correct: decode it! 

Warning! All examples are only suggestions and indications of a possible program organization. 

ANGELANTONI Industrie declaims all responsibility for the use (correct or not correct) of this 

code. 

It is up to the software engineer to modify, complete and test the examples for his own purposes. 


C LANGUAGE 

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The following examples show how to initialize the CRC table and how to compute the CRC bytes to be added at the 

end of the packet to be sent to the controller. 

#define CRC16 0xA001 

static unsigned char TABLE1[256], TABLE2[256]; 

//Initialize tables for the calculation of the CRC 

static void InitCRC() 

{ 

unsigned char i; 

unsigned int mask, crc, mem; 

} 

for(mask=0;mask 8); /* hibyte */ 

} 

//Calculate the CRC 

static unsigned int CalcCRC(unsigned char *buf, unsigned char size) 

{ 

unsigned char car,i; 

unsigned char crc0,crc1; 

crc0 = 0xff; 

crc1 = 0xff; 

for(i=0;i

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The following code is just an example that shows how to elaborate a data block to be transmitted to the chamber 

controller in order to read back others data. 

As explained previously, you have to specify the starting address of the data block and the number of the registers to 

be read. 

QUERY (function 3) 

void ModbusReadStatus(void) 

{ 

int r, n, cmd; 

unsigned char tx[50]; 

//Read 104 words starting at address 2000 

r = 2000; //starting address 

n = 104; //number of registers to read 

tx[0] = 17; //mPLC address 

tx[1] = 3; //Modbus read (function 3) 

tx[2] = (unsigned char)(r >> 8); //first register (HO byte) = 7 

tx[3] = (unsigned char)(r & 0xFF); //first register (LO byte) = 208 

tx[4] = (unsigned char)(n >> 8); //num. of registers (HO byte) = 0 

tx[5] = (unsigned char)(n & 0xFF); //num. Of registers (LO byte) = 104 

ModbusTxMsg(tx, sizeof(tx[0]) * 6); 

} 

//The ModbusTxMsg()function is used to reach the CRC field at the end of 

//the packet and and send packet to the controller. Below there is just 

//a skeleton of a possible way to implement the code. 

memcpy(pData, buffer, size); 

*(unsigned int *)(pData+size) = CalcCRC(pData,size); 

//send data 

In effect, in order to read 104 registers starting from address 2000, the complete packet to be transmitted to the 

controller is as follows: 

tx[0] = 17; 

tx[1] = 3; 

tx[2] = 7 

tx[3] = 208 

tx[4] = 0 

tx[5] = 104 

tx[6] = 70 

tx[7] = 57 

ANSWER ( Function 3 ) 

The PC software waits for the complete packet coming from the controller. As previously seen, a data packet can be 

detected using TIME SYNCHRONIZATION or FRAME SYNCHRONIZATION. 

All data must be converted into a type according to the specifications of controller memory layout. 


VISUAL BASIC 

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We assume you are familiar with VISUAL BASIC 5.0 (or upper) for Windows 95. Only the important sections of code 

are present in the following description. 

CRC CALCULATION 

Private Const CRC16 As Long = 40961 '0xA001 in exadecimal 

Private table1(255) As Byte 

Private table2(255) As Byte 

Private Function calcCrc(buf() As Byte, size As Byte) As Long 

‘Calculation of CRC 

Dim i As Byte 

Dim car As Long 

Dim crc0 As Long 

Dim crc1 As Long 

crc0 = &HFF 

crc1 = &HFF 

For i = 0 To size - 1 

car = buf(i) 

car = car Xor crc0 

crc0 = (crc1 Xor table2(car)) And &HFF 

crc1 = table1(car) 

Next i 

calcCrc = (crc1 * 256 + crc0) And &HFFFF 

End Function 

Public Sub initCrc() 

‘Initialize the tables to use by the calcCrc() function 

Dim i As Byte 

Dim mask As Long 

Dim crc As Long 

Dim mem As Long 

For mask = 0 To 255 

crc = mask 

For i = 0 To 7 

mem = crc And &H1 

crc = crc \ 2 

If mem 0 Then crc = crc Xor CRC16 

Next i 

table2(mask) = crc And &HFF 

table1(mask) = crc \ 256 

Next mask 

End Sub 

The query packet to be sent to the controller is reported below: 

address = 2000 

mbtx(0) = 17 ‘address of µPLC 

mbtx(1) = 3 ‘function number (reading)) 


mbtx(2) = address \ 256 

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‘hi byte (start reg.) 

mbtx(3) = address And &HFF ‘low byte (start reg.) 

mbtx(4) = 0 ‘hi byte (num. reg.) 

mbtx(5) = 104 ‘low byte (num. reg.) 

crc = calcCrc(mbtx(), 6) ‘calculate the CRC 

mbtx(6) = crc And &HFF ‘low byte CRC 

mbtx(7) = crc \ 256 ‘hi byte CRC 

EXAMPLES OF READING AND WRITING QUERY 

In the following section, a dump of data communication is reported in order to see what really happens in a normal 

communication session between master and slave. 

WRITING OPERATION 

Let’s say that we want to send the following configuration to the chamber controller: 

Temperature: 50 Celsius degree 

Relative Humidity: 70% 

Run bit: ON 

Temperature channel: ON 

Re. Humidity channel: ON 

Dedicated contacts: ON for all the eight contacts available 

As described previously, a query packet must be prepared and sent to the chamber controller to write data to the 

specific locations we are interested in. 

When the controller receives this data packet, it decodes it, acts as requested changing the content of the memory 

locations to work with, and answer to the master. 

The answer can be a normal answer packet for the function numer 16, or an error packet if an exception has been 

detected. 

Note also that, if a communication error (frame, parity, overrun or CRC) has been detected by the slave, no answer will 

be sent to the master. 


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> Query sent: 

> 000: 017 0011 mplc address 

> 001: 016 0010 modbus function number 

> 002: 008 0008 memory address high 

> 003: 252 00FC memory address low 

> 004: 000 0000 number of registers high 

> 005: 030 001E number of registers low 

> 006: 060 003C byte count 

> 007: 003 0003 high order data Channels T and RH in ON status 

> 008: 001 0001 low order data Run bit in ON status 

> 009: 000 0000 high order data 

> 010: 255 00FF low order data All dedicated cintacts in ON status 


> 012: 000 0000 low order data 


> 014: 000 0000 low order data 

> 015: 019 0013 high order data Temperature Set: 50 degrees 

> 016: 136 0088 low order data codified as 5000 


> 018: 000 0000 low order data 


> 020: 000 0000 low order data 

> 021: 027 001B high order data Set of RH: 70% 

> 022: 088 0058 low order data codified as 7000 


> 024: 000 0000 low order data 


> 026: 000 0000 low order data 


> 028: 000 0000 low order data 


> 030: 000 0000 low order data 


> 032: 000 0000 low order data 


> 034: 000 0000 low order data 


> 036: 000 0000 low order data 


> 038: 000 0000 low order data 


> 040: 000 0000 low order data 


> 042: 000 0000 low order data 


> 044: 000 0000 low order data 


> 046: 000 0000 low order data 


> 048: 000 0000 low order data 


> 050: 000 0000 low order data 


> 052: 000 0000 low order data 


> 054: 000 0000 low order data 


> 056: 000 0000 low order data 


> 058: 000 0000 low order data 


> 060: 000 0000 low order data 


> 062: 000 0000 low order data 


> 064: 000 0000 low order data 


> 066: 000 0000 low order data 


067: 049 0031 error check 

> 068: 068 0044 error check 

� End packet. 

> Data received: (idx) (dec) (hex) 

> 000: 017 (0011) mplc address 

> 001: 016 (0010) modbus function number 

> 002: 008 (0008) high order address 

> 003: 252 (00FC) low order address 

> 004: 000 (0000) quantity 

> 005: 030 (001E) quantity 

> 006: 128 (0080) error check 

> 007: 193 (00C1) error check 

> End packet. 

READING OPERATION 

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Let’ s say that the following data are returned from the slave to the master: 

Temperature: 137.6 Celsius degree 

Rel. Humidity: 0.0% 

Temperature channel: ON 

Rel. Humidity channel: ON 

Run bit: ON 

Dedicated contacts: ON 

In the example below we read 104 registers, starting at address 2000. Please note that many of the data returned by 

the controller are not used, so it is also possible to read just a sub-block of these registers, containing only the data 

we really need to know. 

See the controller memory map to know more about the reading area. 

> Query sent: 

> 000: 017 0011 mplc address 

> 001: 003 0003 modbus function number 

> 002: 007 0007 memory address high 

> 003: 208 00D0 memory address low 

> 004: 000 0000 number of registers high 

> 005: 104 0068 number of registers low 

> 006: 070 0046 error check 

> 007: 057 0039 error check 

� End packet. 

> Data received: (idx) (dec) (hex) 

> 000: 017 (0011) mplc address 

> 001: 003 (0003) modbus function number 

> 002: 208 (00D0) byte count 

> 003: 053 (0035) mplc addr. 2000 (h.o. data) [ pt100 sensors ] 

> 004: 189 (00BD) 

> 005: 000 (0000) mplc addr. 2001 (h.o. data) 

> 006: 000 (0000) 

> 007: 058 (003A) mplc addr. 2002 (h.o. data) 

> 008: 243 (00F3) 


> 010: 000 (0000) 



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> 012: 000 (0000) 


> 014: 000 (0000) 


> 016: 000 (0000) 


> 018: 000 (0000) 


> 020: 000 (0000) 


> 022: 000 (0000) 


> 024: 000 (0000) 


> 026: 000 (0000) 

> 027: 031 (001F) mplc addr. 2012 (h.o. data) [ analog inputs ] 

> 028: 140 (008C) 


> 030: 000 (0000) 


> 032: 052 (0034) 


> 034: 000 (0000) 

> 035: 030 (001E) mplc addr. 2016 (h.o. data) 

> 036: 025 (0019) 


> 038: 000 (0000) 


> 040: 154 (009A) 


> 042: 000 (0000) 


> 044: 000 (0000) 


> 046: 000 (0000) 


> 048: 000 (0000) 


> 050: 000 (0000) 


> 052: 000 (0000) 


> 054: 000 (0000) 


> 056: 000 (0000) 


> 058: 000 (0000) 


> 060: 000 (0000) 


> 062: 000 (0000) 


> 064: 000 (0000) 


> 066: 000 (0000) 

> 067: 000 (0000) mplc addr. 2032 (h.o. data) [ computed measures ] 

> 068: 000 (0000) 


> 070: 000 (0000) 


> 072: 000 (0000) 


> 074: 000 (0000) 


> 076: 189 (00BD) 


> 078: 000 (0000) 


> 080: 000 (0000) 



- 22 - 

> 082: 000 (0000) 


> 084: 000 (0000) 


> 086: 000 (0000) 


> 088: 000 (0000) 


> 090: 000 (0000) 


> 092: 000 (0000) 


> 094: 000 (0000) 


> 096: 000 (0000) 


> 098: 000 (0000) 


> 100: 000 (0000) 


> 102: 000 (0000) 


> 104: 000 (0000) 


> 106: 000 (0000) 

> 107: 002 (0002) mplc addr. 2052 (h.o. data) [ alarms/messag. ] 

> 108: 000 (0000) 

> 109: 000 (0000) mplc addr. 2053 (h.o. data) [ alarms/messag. ] 

> 110: 000 (0000) 


> 112: 000 (0000) 


> 114: 001 (0001) 

> 115: 003 (0003) mplc addr. 2056 (h.o. data) [ required settings ] 

> 116: 001 (0001) 

> 117: 000 (0000) mplc addr. 2057 (h.o. data) [ required settings ] 

> 118: 255 (00FF) 


> 120: 000 (0000) 


> 122: 000 (0000) 

> 123: 003 (0003) mplc addr. 2060 (h.o. data) [ real settings ] 

> 124: 001 (0001) 

> 125: 000 (0000) mplc addr. 2061 (h.o. data) [ real settings ] 

> 126: 128 (0080) 


> 128: 000 (0000) 


> 130: 000 (0000) 

> 131: 000 (0000) mplc addr. 2064 (h.o. data) [ setpoint readings ] 

> 132: 000 (0000) 


> 134: 000 (0000) 


> 136: 000 (0000) 


> 138: 000 (0000) 


> 140: 000 (0000) 


> 142: 000 (0000) 


> 144: 000 (0000) 


> 146: 000 (0000) 


> 148: 000 (0000) 


> 150: 000 (0000) 



- 23 - 

> 152: 000 (0000) 


> 154: 000 (0000) 


> 156: 000 (0000) 


> 158: 000 (0000) 


> 160: 000 (0000) 


> 162: 000 (0000) 


> 164: 000 (0000) 


> 166: 000 (0000) 


> 168: 000 (0000) 


> 170: 000 (0000) 


> 172: 000 (0000) 


> 174: 000 (0000) 


> 176: 000 (0000) 


> 178: 000 (0000) 


> 180: 000 (0000) 


> 182: 000 (0000) 


> 184: 000 (0000) 


> 186: 000 (0000) 


> 188: 000 (0000) 


> 190: 000 (0000) 


> 192: 000 (0000) 


> 194: 000 (0000) 


> 196: 000 (0000) 


> 198: 000 (0000) 


> 200: 000 (0000) 


> 202: 000 (0000) 


> 204: 000 (0000) 


> 206: 000 (0000) 


> 208: 000 (0000) 


> 210: 000 (0000) 

> 211: 132 (0084) error check 

> 212: 244 (00F4) error check 

> End packet. 


CALCULATED CRC TABLES 

- 24 - 

The following tables contain the CRC values computed using C e Visual Basic code previously reported. These tables 

can be used as riference in case you want to write a program using languages different from those are indicated in the 

examples. 

TABLE 1 

TABLE 2 

0 192 193 1 195 3 2 194 (items from 0 to 7) 

198 6 7 199 5 197 196 4 (items from 8 to 15) 

204 12 13 205 15 207 206 14 

10 202 203 11 201 9 8 200 

216 24 25 217 27 219 218 26 

30 222 223 31 221 29 28 220 

20 212 213 21 215 23 22 214 

210 18 19 211 17 209 208 16 

240 48 49 241 51 243 242 50 

54 246 247 55 245 53 52 244 

60 252 253 61 255 63 62 254 

250 58 59 251 57 249 248 56 

40 232 233 41 235 43 42 234 

238 46 47 239 45 237 236 44 

228 36 37 229 39 231 230 38 

34 226 227 35 225 33 32 224 

160 96 97 161 99 163 162 98 

102 166 167 103 165 101 100 164 

108 172 173 109 175 111 110 174 

170 106 107 171 105 169 168 104 

120 184 185 121 187 123 122 186 

190 126 127 191 125 189 188 124 

180 116 117 181 119 183 182 118 

114 178 179 115 177 113 112 176 

80 144 145 81 147 83 82 146 

150 86 87 151 85 149 148 84 

156 92 93 157 95 159 158 94 

90 154 155 91 153 89 88 152 

136 72 73 137 75 139 138 74 

78 142 143 79 141 77 76 140 

68 132 133 69 135 71 70 134 

130 66 67 131 65 129 128 64 

0 193 129 64 1 192 128 65 (items from 0 to 7) 

1 192 128 65 0 193 129 64 (items from 8 to 15) 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

1 192 128 65 0 193 129 64 


0 193 129 64 1 192 128 65 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

0 193 129 64 1 192 128 65 

0 193 129 64 1 192 128 65 

1 192 128 65 0 193 129 64 

MICROPLC MEMORY LAYOUT VERS. 2.0 

- 25 - 

NOTE: 

It's very important that writing operations in microPLC are correct and right. In effect it is absolutely 

important that the data written to the microPLC are correct from the format point of view and from the 

addresses point of view. 

Wrong data or wrong addresses for data can be very dangeorus for the functionality of the controller. 

It is operator's liability to make sure that all safety conditions are guaranteed, in order to avoid damages to 

the chamber controller and chamber devicecs or to prevent its right functioning through wrong operations. 

ANGELANTONI Industrie doesn't take any liability on itself, neither directly or inderectly, about problems 

caused by bad functioning due to software development based on this manual. 

In the following section the memory layout of the chamber controller version 2.00 is shown 

In this version the entire area available to the user is divided in two different sections, the first of them dedicated only 

for reading and the second one for writing. 

Please, note that the microPLC controller provides a wide range of facilities and only a sub-set of these is really used 

to control Hygros e Challenge chambers (also called “standard chambers”). 

Specifically, standard chambers use 2 regulators (and so only 2 channels for measuring and setting operations). 

Non standard chambers could use more deeply the facilities coming from the microPLC, according to the customer 

requirements. If this is the case, a manual appendix will be available together with this manual, to specify the 

controller memory area really used. 

The following section of this manual only refers to standard chambers, even if the general memory layout is shown. 

The PC software normally reads the reading area in order to know the status (measures, actiovations, alarms) of the 

chamber. 

When a new status for the chamber is required (for example, the user wants to change the temperature set for the 

chamber from 35 to 75 Celsius degree), the PC software makes a query to the microPLC, writing data into the 

writing area. When done, the PC software simply turn back to its normal task: reading from the chamber. 

According to the data sent by the PC, chamber controller will try to act in order to satisfy the user requests, if 

possible. 

A logic layout is shown below: 

PC SOFTWARE 

Fig. 7 System logic layout 

microPLC 

READING 

AREA 

WRITING 

AREA 

Chamber 

control 

logic 


- 26 - 

As already stated, note that if the microPLC is used on chambers different from Challenge and Hygros 

(“standard chambers”), the meanings of some channels could be different from those reported here. 

Whre the DCTC term appears it means that the corrispondent columns of values are relative to the “Salt 

Fogs” systems. 

READING AREA 

The information in this area allows the user to know the general status of the system. 

According to the application to be developed only a part of these information could be necessary. 

Note that measures are multiblied by a factor whose value depends from the parameter. The factor is reported in each 

table (for example: PT100 n. 0 * 100 means that in the memory location the value is the temperature measure for 

PT100 number 0, multiplied by 100). 

PT100 MEASURES 

For Challenge/Hygros chambers the PT100 no. 0 is the probe of dry bulb, and the no. 1 is the probe of wet bulb. 

Note that the PT100 n. 0 is also copied into locatios 2036-2037 (Calculated Input Measures). 

ADDRESS MEANING 

2000-2001 PT100 NO. 0 * 100 

2002-2003 PT100 NO. 1 * 100 

2004-2005 PT100 NO. 2 * 100 

2006-2007 PT100 NO. 3 * 100 

2008-2009 PT100 NO. 4 * 100 

2010-2011 PT100 NO. 5 * 100 

ANALOGIC INPUTS MEASURES 


2012-2013 Low stage suction * 1000 

2014-2015 Low stage discharge * 1000 

2016-2017 High stage suction * 1000 

2018-2019 High stage discharge * 1000 

2020-2021 Analogic input No. 4 * 1 






CALCULATED INPUTS MEASURES 

For standard chambers only 3 parameters are used. Note that the temperature reported below is the same value you can find in 

the PT100 measures table at address 2000; in effect it is the dry bulb temperature. 

Absolute humidity is the absolute value used by the chamber regulator to control the humidity in the chamber. It is normally not 

useful to the operator: Relative humidity and Temperature globally identify the status of the chamber. 


- 27 - 


2032-2033 Relative Humidity % * 100 

2034-2035 Absolute Humidity g/Kg * 10 

2036-2037 Temperature (same as PT100 n. 0) * 100 

2038-2039 Calculated input NO. 3 








- 28 - 

MESSAGES 

The following messages list is general: some of them could not be used in your chamber. Note that messages are 

associated to bits, so the term “2052.3” means “bit number 3 (counting from 0) at address 2052” 


2052.0 Protection switches 

2052.1 Maximum temperature User 

2052.2 Minimum temperature User 

2052.3 Low Stage Massimum pressure 

2052.4 Maximum pressure High Stage 

2052.5 Thermal protection low stage compressor 

2052.6 Thermal protection high stage compressor 

2052.7 Maximum temperature service 

2052.8 Water lack 

2052.9 Safety temperature switches 

2052.10 General power lack 

2052.11 Equipment off 

2052.12 Low stage oil pressure switch 

2052.13 High stage oil pressure switch 

2052.14 Maximum temperature glycol 

2052.15 Minimum level glycol 

2053.0 Maximum temperature Steam generator 

2053.1 Inverter Alarm 

2053.2 Air lack 

2053.3 Flow switch 

2053.4 Minimum temperature glycol 

2053.5 Minimum pressure pump glycol 

2053.6 Maximum temperature discharge low stage 

2053.7 Maximum temperature discharge high stage 

2053.8 Door open 

2053.9 Minimum level water 

2053.10 Air differential pressure switch 

2053.11 Smoke detector 

2053.12 Salty solution lack 

2053.13 

2053.14 

2053.15 

2054.0 

2054.1 

2054.2 

2054.3 

2054.4 

2054.5 

2054.6 

2054.7 

2054.8 

2054.9 

2054.10 

2054.11 

2054.12 

2054.13 

2054.14 

2054.15 

2055.0 Critical alarm (The ladder writes) 

2055.1 Power lack (The ladder writes) 

2055.2 Resume from critical alarm (The firmware writes) 

2055.3 

2055.4 programme abort into execution (The firmware writes) 

2055.5 Natural end of the programme into execution (The firmware writes) 

2055.6 Resume time elapsed 

2055.7 Critical deviation 

2055.8 Not critical deviation 

2055.9 

2055.10 


2055.11 

2055.12 

2055.13 

2055.14 

2055.15 

- 29 - 

USER AND REAL SETTINGS 

It is important to well understand the logic operations in sending a new data configuration (we intend a new group of 

data the chamber has to use, for example new temperature settings, new RUN/STOP status and so on). 

In effect, this operation can be seen as composed of 2 different stages: 

1. the user prepares the new set of data and send it to the controller (user settings) 

2. the controller acts properly to work with the new set (if possible) (real settings) 

From the above description you can understand that the final result of the entire operation can or cannot be the same 

as requested by the user depending on the chamber and controller status. For example, suppose that an alarm is 

present in the system, so the chamber is in alarm condition. If the user send a new set of data in order to change the 

status of the RUN bit (the user want the chamber running), no action will take place, beacuase of the alarm. 

In other words, we have a “user setting” group of data in which the RUN bit is in ON status, while the same bit in the 

“real settings” will be in OFF status. 

USER SETTINGS 

ADDRESS CHAMBERS DCTC 

2056.0 Run Run 

2056.1 Alarm Reset Alarm Reset 

2056.2 Program(1) Manual(0) Programme(1) Manual(0) 

2056.3 Local(1) Remote(0) Local(1) Remote(0) 

2056.4 Pause Pause 

2056.5 Freeze Freeze 

2056.6 

2056.7 

2056.8 Channel activation 0 (Temperature) Channel activation 0 (Temperature) 

2056.9 Channel activation 1 (Rel. Humidity) Channel activation 1 (Rel.Humidity) 

2056.10 Channel activation 2 Channel activation 2 (Humid. Temperature) 

2056.11 Channel activation 3 Channel activation 3 (H2O temperature) 

2056.12 Channel activation 4 Channel activation 4 




2057.0 Forced Dehumidification Spraying with humidified air 

2057.1 Vibrator Spraying with not humidified air 

2057.2 DUT Purging with air (Centrifugal) 

2057.3 U.V. Lamp Dry (Compressed air) 

2057.4 Water recharge Flooding with Air temperature control 

2057.5 Flooding with air+water control (Refrigerator) 

2057.6 

2057.7 Humidity special control Humidity special control 

2057.8 Aux 1 Aux 1 

2057.9 Aux 2 Aux 2 

2057.10 Aux 3 Aux 3 

2057.11 Aux 4 Aux 4 

2057.12 Aux 5 Aux 5 

2057.13 Aux 6 Aux 6 

2057.14 Aux 7 Aux 7 

2057.15 Aux 8 Aux 8 

2058 

2059 


- 30 - 


- 31 - 

REAL SETTINGS 



2060.1 Alarms reset Alarms reset 

2060.2 Programme(1) Manual(0) Programm(1) Manual(0) 




2060.6 

2060.7 

2060.8 Channel activation 0 (Temperature) Channel activation 0 (Temperature) 

2060.9 Channel activation 1 (Rel. Humidity) Channel activation 1 (Rel.Humidity) 

2060.10 Channel activation 2 Channel activation 2 (Humid. Temperature) 

2060.11 Channel activation 3 Channel activation 3 (H2O Temperature) 





2061.0 Forced dehumidification Spraying with humidified air 


2061.2 DUT Purging with air (Centrifugal) 

2061.3 U.V. Lamp Dry (compressed air) 

2061.4 Water recharge Flooding with air temperature control 

2061.5 Flooding with air and water temperature control 

2061.6 

2061.7 Special humidity control Special humidity control 

2061.8 Aux 1 Aux 1 

2061.9 Aux 2 Aux 2 

2061.10 Aux 3 Aux 3 

2061.11 Aux 4 Aux 4 

2061.12 Aux 5 Aux 5 

2061.13 Aux 6 Aux 6 

2061.14 Aux 7 Aux 7 

2061.15 Aux 8 Aux 8 

2062 

2063 


- 32 - 

SETPOINTS READING 

The values reported here are the setpoint values actually used by the regulators inside the chamber controller. 

Note that the final setpoint equals the current setpoint only in case of maintenances or slopes at max. speed. 

They will be different in case of controlled slopes (gradient different from 0). 

For standard chambers (Challenge and Hygros) the values are multiplied by 100. 

As previously stated, in the standard chambers channel 0 is the Temperature regulator, while channel 1 is the Rel. 

Humidity regulator. 


2064-2065 User Final Setpoint Channel 0 * 100 

2066-2067 Current Setpoint User Channel 0 * 100 

2068 Gradient Channel 0 * 100 

2069-2070 Final Setpoint user Channel 1 * 100 

2071-2072 Current Setpoint user Channel 1 * 100 


















2101-2102 Current Setpoint user channel 7 * 100 

2103 Gradient channel 7 * 100 


- 33 - 

TEST PROGRAM STATUS 

All information on the test cycle status actually running are reported in this section. 

Note that the information relative to the table jumps (loop, locations of memory from 2127 to 2146) are divided into 

high byte (to the left) and low byte (to the right) and each byte has the meaning reported in the corresponding 

position. 

Note that “segment flags” and “control flags” are variables used internally by the chamber controller during the 

execution of a cycle. These flags are not useful to the normal user. 


2104 NO. Of segments 

2105 First segment 

2106 Current segment 

2107-2108 Current segment duration (seconds) 

2109-2110 Current segment elapsed time (seconds) 

2111-2112 Current segment remaining time (seconds) 

2113-2114 Test program elapsed time (seconds) 

2115 Segment Flags 

2116 Control Flags 

2117 Channel 0 Flags 








2125 Total loop of the entire test program 

2126 Current Loop of the entire test program 

2127 Internal Loop 01: FINAL SEGMENT INITIAL SEGMENT 

2128 Internal Loop 01: TOTAL REPET. CURRENT REPET. 




















- 34 - 

WRITING AREA 

This is the “control” area wherein the user must write the new operative configuration he wants for the system. The 

term “new operative configuration” means the desired status of the relays, setpoints, gradients and channels in order 

to obtain a certain behaviour from the chamber. 

The setpoint and gradient values of the various channels must be multiply by 100. So, for instance, if you want to set 

the value of 75.0 degrees with gradient of 1.5 Celsius degrees/minute, it will be necsssary to write 7500 and 150 in the 

correspondent locations. 

As already stated, channel 0 refers to the temperature channels. 



2300.1 Alarms Reset Alarms Reset 

2300.2 Program(1) Manual(0) Programme(1) Manual(0) 




2300.6 

2300.7 

2300.8 Activation Channel 0 (Temperature) Activation Channel 0 (Temperature) 

2300.9 Activation Channel 1 (Rel. Humidity) Activation Channel 1 (Rel.Humidity) 

2300.10 Activation Channel 2 Activation Channel 2 (Humid. Temperature) 

2300.11 Activation Channel 3 Activation Channel 3 (H20 Temperature) 

2300.12 Activation Channel 4 Activation Channel 4 




2301.0 Forced Dehumidification Spraying with humidified air 


2301.2 DUT Purging with air (Centrifuge) 

2301.3 U.V. Lamp Dry (Compressed air) 

2301.4 Water exchange Flooding with Air temp. Control 

2301.5 Flooding with Air+water control (Refrigerator) 

2301.6 

2301.7 Humidity special control Humidity special control 

2301.8 Aux 1 Aux 1 

2301.9 Aux 2 Aux 2 

2301.10 Aux 3 Aux 3 

2301.11 Aux 4 Aux 4 

2301.12 Aux 5 Aux 5 

2301.13 Aux 6 Aux 6 

2301.14 Aux 7 Aux 7 

2301.15 Aux 8 Aux 8 

2302 

2303 

2304-2305 Final Setpoint user channel 0 * 100 Final Setpoint user channel 0 * 100 

2306 Gradient channel 0 * 100 Gradient channel 0 * 100 





2313-2314 Final Setpoint user channel 3 * 100 Setpoint finale utente canale 3 * 100 

2315 Gradient channel 3 * 100 Gradiente canale 3 * 100 

2316-2317 Final Setpoint user channel 4 * 100 Setpoint finale utente canale 4 * 100 







2327 Gradient Channel 7 * 100 Gradient Channel 7 * 100 


- 35 - 

2328 Initial Segment Initial Segment 

2329 Cycle repetition Cycle repetition 


NOTE 

- 36 - 

� The ALARMS RESET operation is made setting to 1 the corresponding bit. The microPLC will provide in 

automatic mode to force it to 0 after few seconds. 

� The bit LOCAL/REMOTE, PAUSE and FREEZE are reserved and not actually used. It is advisable to force them 

to 0. 

� In order to work, a regulator needs both the setpoint value and the enable bit in ON status (bit 2300.8 and 

following). For instance, the temperature controller (Channel 0) will be in stand-by and will not execute any 

regulation in case that the enabling bit (bit 2300.8) is equal to 0. 

� Non standard chambers (other than Hygros and Challenge) could have differencies in some of the parameters 

reported in this document. An appendix is normally shipped with chamber in order to focus on these differencies. 


- 37 - 

APPENDIX A: CONNECTION OF A SERIAL CABLE 

In the following are described the connections required to have a serial connection between chamber and PC. 

In the following drawing the female connector on the left must be connected to the RS232/485 connector of the 

chamber. 

TYPE 9 PIN CONNECTOR – RS232 

Fig. 8 Serial cable

Serial Communications Protocol Specifications - Swissvacuum.com

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