Chengdu Ebyte Electronic Technology Co.,Ltd E851-RTU(4440-ETH) User Manual
Copyright ©2012–2019, Chengdu Ebyte Electronic Technology Co.,Ltd
4.2. Basic functions of IO
4.2.1. Switch DO Output
4.2.1.1 Read Switch DO Output
Function code: 01, read coil status
Address range: 00017 (0x0010) ~ 00020 (0x0013)
Explanation: When equipment relay passive output and coil is not powered on, relay NC port and COM port are usually
closed, NO port and COM port are often open, with a value of 0; when coil is energized, the phenomenon is opposite,
relay NC port and COM port are disconnected, NO port and COM port are closed, with a value of 1. Query relay status
by instruction.
Example:
Read the 4-way switch output state, assuming a return value of 03, corresponding to the binary bit 0000 0011, the lower
four bits and four bits represent the switch output state, which in turn is DO4, DO3, DO2, DO1.
Modbus RTU protocol reads switching output:
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