User Manual

4 ADAM-4572 User's Manual
Ethernet Modbus/TCP
P
C
P
C
ADAM
Ethernet
RS-232/485/422
ADAM
Ethernet
RS-232/485/422
ADAM-4572 ADAM-4572
Modbus/RTU Modbus/ASCII
ADAM-5511
PLC
ADAM-5000/MOD
P
C
3rd party device (RTU)
Figure 1-1: Modbus System Architecture
1.2.2 Modbus/RTU
The Modbus/RTU protocol defines how a “master” device polls one or
more “slave” devices to read and write data in real-time over RS-232,
RS-422, or RS-485 serial data communication.
When using RTU mode, each 8-bit byte in a message contains two 4-bit
hexadecimal characters. The main advantage of this mode is that its greater
character density allows better data throughput than ASCII mode for the
same baud rate. Nevertheless, each message must be transmitted in con-
tinuous stream.