Despatch Protocol Plus Modbus Communications - Manual (Page 8)

Chromalox Instruments and Controls
A-51643 Rev. 6 10/06/03 2
2 Communications Specifications
2.1 Support Specifications
Device Support: Slave only.
Slave ID Code (Identifies Product Line): 1.
Transmission Mode: RTU mode only.
Communication Medium: RS232, RS422, or RS485.
Address Support: 1 – 247.
Baud Rate: 2400, 4800, 9600, 19.2K, 38.4K
Parity: None, Even, or Odd.
2.2 Timing Specifications
Message Framing: Silent period of at least 3.5 character times before the first character and after the last
character of the message.
Character Framing: No more than 1.5 character times of silence between received and transmitted
characters.
Message Timeout (Query Response Time): Response to queries will be made within 1 sec.
2.3 Wiring
Figure 1: RS232 Wiring
Rcv
Xmit
Gnd
Master Device Xmit
Rcv
Gnd
3
2 1
Protocol™ Plus DB-9 Connector
Rcv
Xmit
Gnd
2
3
5
2
3
7
DB-25
DB-9
Protocol™ Plus Connector
3
5 5
Rcv
Xmit
Gnd