Monroe Electronics Electrostatic Fieldmeter - Static Monitor - model 177A - Manual (Page 49)

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177A reply to read coil:
Unit# command # of data Coil Value crcH crcL
1-255 0x01 1 0=Off, 0xff=On
Write Channel LEDs or Relays (write coil):
From Master (PC software or PLC):
Unit# Command
CoilAdrH CoilAdrL New Value 0 crcH crcL
1-255 0x05 0 0-24 0=Off, 0xff=On
The request consisted of the Unit address and the command code 05 followed by a 2 byte starting
address, specifying the variable to be set, a data byte, specifying the binary value to set ( ON = 0xff,
OFF = 0 ) and an additional byte always set to 0.
177A reply to write single coil is identical to the received packet:
Unit# Command
CoilAdrH CoilAdrL New Value 0 crcH crcL
1-255 0x05 0 0-24 0=Off, 0xff=On
Read Channel display (read register):
From PC or PLC:
Unit# Command
RegAdrH RegAdrL LenH LenL crcH crcL
1-255 0x03 0 0-3 0 1
RegAdrL is as follows:
0 Channel 1
1 Channel 2
2 Channel 3
3 Channel 4
177A reply:
Unit# Command # of data dataH dataL crcH crcL
1-255 0x03 1 ## ##
Write Channel display (write register):
From PC or PLC:
Unit# Command RegAdrH RegAdrL dataH dataL crcH crcL
1-255 0x06 0 0-3 ## ##
177A reply to write single Register is identical to the received packet:
Unit# Command RegAdrH RegAdrL dataH dataL crcH crcL
1-255 0x06 0 0-3 ## ##
Note:
If the Unit# is 0, the 177A units will execute the Write-Coil and Write-Register commands, but No reply.