Omega OME-ET-7000 Series, Руководство пользователя

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4.5.3. 03 (0x03) Read Holding Registers
This function code is used to read the contents of a contiguous block of holding
registers in an OME-ET-7000/OME-PET-7000 module. The Request PDU specifies
the starting register address and the number of registers. In the PDU Registers are
addressed starting at zero.
The register data in the response message are packed as two bytes per register,
with the binary contents right justified within each byte. For each register, the first
byte contains the high order bits and the second contains the low order bits.
Here is an example of a request to read analog outputs of
OME-ET-7026/OME-PET-7026 module:
Request Response
Field Name (Hex) Field Name (Hex)
MBAP Header
01
MBAP Header
01
02 02
00 00
00 00
00 00
06 07
Unit Identifier 01 Unit Identifier 01
Function Code 03 Function Code 03
Starting Address Hi 00 Byte Count 04
Starting Address Lo 00 Register value Hi (AO0) 02
Quantity of Outputs Hi 00 Register value Lo (AO0) 2B
Quantity of Outputs Lo 02 Register value Hi (AO1) 00
Register value Lo (AO1) 64
The contents of AO0 are shown as the two byte values of 02 2B hex, or 555 decimal.
The content of AO1 are 00 64, or 100 decimal.