snap ethernet-based i/o units protocols and programming guide

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CHAPTER 2: OVERVIEW OF PROGRAMMING If you are configuring points in your own program, to use a simple quadrature counter you need to configure the point feature for only one of the two points. To do so, set the point feature to the value 04 (quadrature counter). You can read the quadrature count from either point by reading the point’s counter data. Using a Quadrature Counter with an Index To use a quadrature counter with an index, configure the point feature in ioManager’s Inspect window, not in the configuration file, or configure the point feature in your program. Configure the point feature for either Point A (quadrature channel phase A) or Point B (quadrature channel phase B). Point A must be an even-numbered point and point B an odd-numbered point. Configure the point feature for either point A or point B in the following format (hex): XXGG0004. XX is the index point number, which can be any point except A or B and can be used for only one quadrature input pair. GG is the index trigger edge: use 01 to trigger on a rising edge, or 02 to trigger on a falling edge. Once you have configured Point A or Point B, the index point is automatically configured in the following format (hex): QQGG0041, where QQ is the point number of point A or B and GG is the index edge. To read the quadrature count, read the counter data for any of the three points, depending on what you need. Points A and B will show the current quadrature count; the index point will show the quadrature count since the index was triggered. The following table summarizes point feature configuration and behavior of the three points. Point feature format: XXGG0004 XX = index point GG = index edge (01 = rising edge, 02 = falling edge) Point numbers allowed: Even point numbers 0–30 Counter data shows: Current quadrature count 22 SNAP Ethernet-Based I/O Units Protocols and Programming Guide Point A Point B Index Point Same as A; configure A or B Odd point numbers 1–31 Current quadrature count Counter data resets upon: Read & Clear Read & Clear Index edge QQGG0041 (automatically configured) QQ = point A or B GG = index edge (01 = rising edge, 02 = falling edge) Any point except A or B Quadrature count upon index edge Read & Clear
Watchdog (Digital and Analog Points) CHAPTER 2: OVERVIEW OF PROGRAMMING You can set a watchdog on a SNAP Ethernet-based I/O unit to monitor communication with the PC or other host device. If the host does not write data to the brain for the length of time set in the watchdog, the I/O unit automatically sets designated digital and analog I/O points to the values you have determined. A watchdog helps make sure that a communication failure doesn’t result in disaster. If communication fails between the host and the I/O unit controlling a process, the watchdog makes sure the process is automatically brought to a safe state. For example, a valve could automatically close to avoid completely emptying a tank. You can set up a watchdog when configuring digital points or analog points, either in ioManager or in your program. Scaling (Analog Points) You can scale analog input or output points to match your needs. For example, you can scale a -5 V to +5 V input point to reflect 0% to 100%. Point types may be unipolar or bipolar. Examples of Unipolar Points Examples of Bipolar Points 4–20 mA analog output -25 mV to +25 mV analog input 0–10 A RMS analog input -10 to +10 VDC analog output Unipolar and bipolar points are scaled in the same way, with the lowest reading reflecting the low scale and the highest reading reflecting the high scale. Here are examples: Unipolar Input Point Bipolar Input Point Low scale High scale Low scale High scale Actual reading 0 mA 20 mA -5 V 0 V +5 V Scaled for percentage 0% 100% 0% 50% 100% Scaled for counts* -25,000 +25,000 -25,000 0 +25,000 *Counts for input points always range -25,000 to +25,000. Unipolar Output Point Bipolar Output Point Low scale High scale Low scale High scale Actual reading 4 mA 20 mA -10 VDC 0 VDC +10 VDC Scaled for percentage 0% 100% 0% 50% 100% Scaled for counts* 0 4,095 0 2,047.5 4,095 *Counts for output points always range 0–4,095. To scale an analog point, see the instructions in the ioManager User’s Guide. SNAP Ethernet-Based I/O Units Protocols and Programming Guide 23
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Page 3 and 4: Table of Contents Chapter 1: Introd
Page 5 and 6: Non-velocity Algorithms............
Page 7 and 8: Disconnecting......................
Page 9 and 10: Data Logging Configuration—Read/W
Page 11 and 12: Chapter 1 Introduction CHAPTER 1 We
Page 13 and 14: About this Guide CHAPTER 1: INTRODU
Page 15 and 16: For Help CHAPTER 1: INTRODUCTION If
Page 17 and 18: FEATURE CHAPTER 1: INTRODUCTION Ema
Page 19 and 20: CHAPTER 1: INTRODUCTION This task C
Page 21 and 22: CHAPTER 2 Chapter 2 Overview of Pro
Page 23 and 24: Referencing SNAP I/O Points CHAPTER
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Page 29 and 30: I/O Point Types CHAPTER 2: OVERVIEW
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Page 45 and 46: Streaming Data CHAPTER 2: OVERVIEW
Page 47 and 48: Logging Data Area Number of Bytes I
Page 49 and 50: Using PID Loops What is a PID? CHAP
Page 51 and 52: Equations Common to All Algorithms
Page 55 and 56: CHAPTER 3 Chapter 3 Using the SNAP
Page 57 and 58: CHAPTER 3: USING THE SNAP ETHERNET
Page 63 and 64: Environment Visual Basic 6 Internet
Page 65 and 66: MemMap Example Code CHAPTER 3: USIN
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CHAPTER 3: USING THE SNAP ETHERNET
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CHAPTER 3: USING THE SNAP ETHERNET
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GetLastStreamStandardBlock (ActiveX
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CHAPTER 4 Chapter 4 Using the IEEE
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CHAPTER 4: USING THE IEEE 1394-BASE
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Bytes 0-3 Bytes 4-7 Bytes 8-11 Byte
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Bytes 0-3 Bytes 4-7 Bytes 8-11 The
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Bytes 0-3 Bytes 4-7 Bytes 8-11 Byte
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Read and clear latches for individu
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Scaling CHAPTER 4: USING THE IEEE 1
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Read and Write Packet Structure Par
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CHAPTER 5 Chapter 5 Advanced Modbus
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CHAPTER 5: ADVANCED MODBUS PROGRAMM
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APPENDIX A Appendix A SNAP Ethernet
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Status Area Read—Read Only This i
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Date and Time Configuration—Read/
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Security Configuration—Read/Write
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Serial Module Configuration—Read/
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Wiegand Serial Module Configuration
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SNMP Configuration—Read/Write (Do
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Starting Address Length Type Descri
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Digital Point Read—Read Only NOTE
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Analog Point Read—Read Only See
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Analog and Digital Point Configurat
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Digital Events and Reactions—Read
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Analog Point Calculation and Set—
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Analog Read and Clear/Restart—Rea
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Serial Event Configuration—Read/W
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Data Log—Read/Write (Does not app
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Appendix B Table of Offsets Introdu
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Module Point (Decimal) Point (Hex)
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Index A access, setting up SNMP sec
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error codes IEEE 1394-based protoco
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O off-latch, 20 offset, 24 IEEE 139
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