Serial Communications Protocol Specifications - Swissvacuum.com

mbtx(2) = address \ 256
- 18 -
‘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.
Serial communications protocol vers. 2.02 Angelantoni Industrie Spa Massa Martana (PG) Italy