Thermo Scientific 146i, Инструкция по эксплуатации

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MODBUS Protocol
Function Codes
Thermo Fisher Scientific Model 146 i Instruction Manual C-3
The function code is a single byte in length. The following function codes
are supported by the instrument:
Read Coils : 0x01
Read Inputs
: 0x02
Read Holding Registers
: 0x03
Read Input Registers
: 0x04
Force (Write) Single Coil
: 0x05
Read Exception Status
: 0x06
If a function code is received that is not in this list, an invalid function
exception is returned.
The data field varies depending on the function. For more description of
these data fields, see “Function Codes” below.
In MODBUS over Serial an error check is included in the message. This is
not necessary in MODBUS over TCP/IP because the higher-level protocols
ensure error-free transmission. The error check is a two-byte (16 bit) CRC
value.
This section describes the various function codes that are supported by the
Model 146
i .
Read Coils / Inputs read the status of the digital outputs (relays) in the
instrument. Issuing either of these function codes will generate the same
response.
These requests specify the starting address, i.e. the address of the first
output specified, and the number of outputs. The outputs are addressed
starting at zero. Therefore, outputs numbered 1–16 are addressed as 0–15.
The outputs in the response message are packed as one per bit of the data
field. Status is indicated as 1 = Active (on) and 0 – Inactive (off). The LSB
of the first data byte contains the output addressed in the query. The other
outputs follow toward the high end of this byte, and from low order to
Function Code
Data
Error Check
Function Codes
(0x01/0x02) Read Coils /
Read Inputs