Automatic Heating BCM Manuale di istruzioni per l'uso - Pagina 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

B-1.2

Modbus Support Requirements

The Modb

us Netwo k must confor

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