D.2 Commands
Read Holding Registers
The response to a read request is in the following format:
<Slave address>3<Register count (MSB)><Register count (LSB)><Data><CRC (MSB)><CRC (LSB)>
Where:
Slave address As general command format.
Register count As general command format.
Data 4 - 248 bytes of data, representing 1 - 62 floating point numbers in IEEE
format. The “Endian” structure can be selected on the Modbus Serial
Communications menu. Big Endian means that the MSB byte of the IEEE
value is at the right end of the four bytes; Little Endian means it is at the
left.
CRC As general command format.
Write Holding Register
The only supported use for this command is to set the instrument into a calibration state.
Where:
Start register MSB 1
Start register LSB 170
Register count 2
Write Data bytes The IEEE representation of 0, 1, 2, or 3
0 puts the instrument into Measure mode (0,0,0,0)
1 puts the instrument into Cycle mode (63,128,0,0)
2 puts the instrument into Zero mode (64,0,0,0)
3 puts the instrument into Span mode (64,64,0,0)
The response to a write request is to return the first six bytes of the initiating write request.
Error
An error will be returned in the following format:
<Slave address><Function code><Exception code><CRC (MSB)><CRC (LSB)>
Slave address As general command format.
Function code The initiating command’s function code + 128; so either 131 (read) or
144 (write).
Exception code The error code (see table below).
To Next Page
Loading...
