CHAPTER 13 RS-485 COMMUNICATIONS

7. Communitacation methods

<Unicast method>

Messages are sent in the following order in this method: (1)  (2)  (3)  (4)  (5)  (6).

Host controller

(master)

(1) Transmission message

(3) Transmission

message

(2) Response message

(4) Response

message

(6) Response message

(5) Transmission

message

<Broadcasting method>

A transmission message is sent to slaves simultaneously in this method. No response message

is sent back.

Host controller

(master)

(1) Transmission message

(1) Transmission

message

(1) Transmission message

13

Modbus RTU Communications 13-31