Automatic Heating BCM Manuel d'utilisation - Page 9

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APPENDIX B
BOILER COMMUNICATIONS MODULE (BCM)
B-1
BCM MODBUS COMMUNICATION & SUPPORT REQUIREMENTS
The Modbus communication support requirements incorporated in the BCM are as follows:
B-1.1
Function Codes
The BCM supports the Modbus Function Codes SHOWN IN T able B-1.
FUNCTION CODE
03
04
06
B-1.2
Modbus Support Requirements
The Modb
us Netwo k must confor
r
CHARACTERISTIC
Communication Medium
EMS Master to BCM Slave
RS 485 Alowable Cable Length
Address Support From Master EMS
T rasmission Mode Support
Timing specifications:
Baud Rate:
Data Framing:
Message Framing:
Character Framing:
Heartbeat Timeout:
Table B-1. Supported Modbus Function Codes
DESCRIPTION
Read up to 8 contiguous Holding Registers
Read up to 8 contiguous Address Registers
Write a single 16 bit Register
m to the suppor
t requirements listed in T able B-2.
Table B-2. Modbus Support Requirements
RS485 2-Wire Differential Bus With Shield
4000 Feet Maximum
1 to 9 via Address Select Switch (SW1)
RTU (Remote T erminal Unit)
Fixed at 9600
8 data bits, no parity, 1 stop bit
Silent period of at least 3.5 character times Before first
character and After last character
No more than 1.5 character times of silence between
received and transmitted characters
Adjustable (0 or 1 – 240 seconds)
DESCRIPTION
9