IRIS P522 manual Module Communications, Modbus Communication, Introduction, Communication Setting

IRIS MODEL P522 APPLICATION MANUAL

The BASIC BURNER START CIRCUIT shown in Figure 12 is a basic circuit requiring only two pieces of external hardware for each burner:

1.Master Relay with at least two nor- mally-open contacts rated for load.

2.DADE Timer, with two instant close/ timeout open contacts.

* * *

1.Bryant, Design of Fail-Safe Control Systems, Power, January, 1976.

2.Bryant, Is Your Plant’s Control Sys- tem Safe?, Power, August, 1979.

3Fischer, Are PLCs Suitable for Emer- gency Shut-Down Systems?, Presented at 43rd symposium for the process in- dustries, Texas A & M University, 1988.

MODULE COMMUNICATIONS

The P522 communicates with any host computer that has an RS-232 serial I/O port and supports ASCII character code transmission at 4800 baud (or, in cur- rent revisions of the processor chip, at 4800 or 9600 baud). The baud rate is displayed with the module address in the current versions (see SETTING AD- DRESSES, section). The data transmitted to and from the P522 is over two twisted pairs that are dif- ferentially driven and received according to the RS- 422 standard. The differential mode allows long wire runs in harsh, electrical environments.

MODBUS COMMUNICATION

Modbus Communication for IRIS P522 Flame Moni- toring System Signal Processor.

Introduction

Modbus Communication protocol allows the P522 to communicate with any process controllers or hu- man-interface host computers that support this pro- tocol. The P522 processor status and settings are organized as 23 4X holding registers and five 0X

discrete registers. For more information on Modbus protocol, please refer to Modicon’s Modbus Proto- col Reference Guide (PI-MBUS-300 Rev E).

Communication Setting

P522 can communicate only in Modbus RTU mode, with the following configuration:

·9600 baud

·8 data bits

·no parity

·1 stop bit

The factory default of a P520/P522 station number is 0. It is important to change the station number so that there is no duplicate stations. To change or check the station number:

·Press and hold Reset button for 4 seconds.

·The 4 LED digits will show the baud rate and the station number. The 2 leftmost digits are the baud rate (96 or 48); the 2 rightmost digits are station number from (0 to 63).

·Press up/down button to change the station number.

·Press Store button to save station number.

Protocol Detect

P522 with firmware version 5.0 still supports the existing IRIS protocol. After power-up, processor will listen for both protocols. Once the protocol has been detected, communication must remain in this protocol until the unit is powered off.

MODBUS RTU Function Supported

Four Modbus functions are supported:

·01 Output Coil Read

·03 Holding Register Read

·06 Preset Single Holding Register

·16 Preset Multiple Holding Register

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