CTH200 Series PLC User Manual
A.3 CT_MODBUS Library Function Explanation
【Modbus address】
Modbus addresses are typically 5 - or 6-character values containing data type and offset. The
first one or two characters determine the data type, and the last four characters match the data
type. The Modbus master station maps this address to correct function.
Modbus slave station instruction supports the following addresses: 00001 to 00128 are the actual
output, corresponding to Q0.0--Q15.7; 10001 to 10128 are actual inputs corresponding to I0.0 --
I15.7; 30001 to 30032 are analog input registers corresponding to AIW0 to AIW62; 40001 to
4XXXX is the holding register, corresponding to V memory area.
All Modbus addresses are numbered from 1. The following table shows the correspondence
between Modbus addresses and CTH200 addresses. The Modbus slave protocol allows you to
limit the number of inputs, outputs, analog inputs, and holding registers (V zones) that Modbus
master can access.
【Using Modbus slave station protocol instructions】
※ CT_MODBUS slave station protocol instructions occupy CTH200 CPU resource
1) According to different Modbus protocol libraries, the FPORT 0 or 1 is used as the slave station
protocol the condition that cannot be used for any other purpose, including communication with
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