ICP DAS USA tET Series, User Manual

Page: 78 / 118

Ethernet I/O Modules
1. Net ID (Station Number)
The first byte in the frame structure of a Modbus RTU query is the receiver’s address. A valid
address is in the range of 0 to 247. Address 0 is used for general broadcast, while addresses 1 to 247
are given to individual Modbus devices.
2. Function Code
The second byte in the frame structure of a Modbus RTU query is the function code, which describes
what the slave device is required to do. Valid function codes are between 1 and 255. To answer the
query, the slave device uses the same function code as contained in the request. The highest bit of the
function code will only be set to ‘1’ if an error occurs in the system. In this way, the master will know
whether the message has been transmitted correctly or not.
Section Code Function
Reference
(Address)
6.2.1
01 (0x01)
Read the Status of the Coils (Readback DOs) 0xxxx
6.2.2 02 (0x02) Read the Status of the Input (Reads DIs) 1xxxx
6.2.3 03 (0x03) Read the Holding Registers (Readback AOs) 4xxxx
6.2.4 04 (0x04) Read the Input Registers (Reads AIs) 3xxxx
6.2.5 05 (0x05) Force a Single Coil (Writes DO) 0xxxx
6.2.6 06 (0x06) Preset a Single Register (Writes AO) 4xxxx
6.2.7 15 (0x0F) Force Multiple Coils (Writes DOs) 0xxxx
6.2.8 16 (0x10) Preset Multiple Registers (Writes AOs) 4xxxx
ICP DAS CO., LTD. PETL/tET/tPET DIO Series User Manual, Ver. 2.1, Sep. 2014, Page: 78
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