Automation Direct D0-DCM, Руководство пользователя

Страница: 65 / 70

MODBUS R
T
U
D0–DCM with
Installation and
5–9
D0–DCM Using MODBUS
DL05/06 Data Communications Module, 1st Edition, 08/05
Network Master Operation
This section describes how the DL05/06 CPU can serve as a master on a MODBUS
RTU network using the D0–DCM. This section discusses how to design the required
ladder logic for network master operation.
Slave #1 Slave #3
Master
MODBUS RTU Protocol
Slave #2
MODBUS Slaves
When using the DCM as a master on the
network, you use simple RLL instructions to
initiate the requests. The WX instruction
initiates network write operations, and the RX
instruction initiates network read operations.
Before executing either the WX or RX
commands, we need to load data related to
the read or write operation onto the CPU’s
accumulator stack. When the WX or RX
instruction executes, it uses the information
on the stack combined with data in the
instruction box to completely define the task.
Slave
Master
WX (write)
RX (read)
Network
The D0–DCM supports the following MODBUS function codes when acting as a
MODBUS RTU master.
MODBUS
Function Code
Function DL05/06
Data Types Available
01 Read Output Table Y, C, T, CT
02 Read Input Table X, SP
03 Read Holding Registers (when addressing
mode is 584/984, this function is used to ac-
cess analog output registers) V
06 Preset Single Registers V
15 Force Multiple Outputs Y, C, T, CT
16 Preset Multiple Registers V
Note: The D0–DCM, as a master, does not support function code 4. Thus, 30001
address ranges cannot be read from a slave device.
MODBUS Function
Codes Supported