GASSONIC OBSERVER-i
54
6.4.2. Modbus Write Response Message
Byte
Modbus
Range
Referenced to
Gassonic
Observer-i
1
st
Slave
Address 1-247*
(Decimal)
Gassonic Observer-i ID (Address)
2
nd
Function Code
06
Preset Single Register
3
rd
Register
Address
Hi**
00
Not used by Gassonic Observer-i
4
th
Register Address
Lo**
00-FF (Hex)
Gassonic Observer-i Commands
5
th
Preset Data Hi
00-FF (Hex)
Gassonic Observer-i Hi Byte
Command Data
6
th
Preset Data Lo
00-FF (Hex)
Gassonic Observer-i Lo Byte
Command Data
7
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
8
th
CRC Hi
00-FF (Hex)
CRC Hi Byte
Table 9: Modbus Write Response Message
NOTE*:
Address 0 is reserved for broadcast mode and is not supported at this time.
NOTE**:
Start Address can be a maximum of 247 Address Locations (0000-0x00F7).
6.4.3. Function Codes Supported
Function Code 03 or 04 (Read Holding Registers) is used to read status from the slave unit. Function
Code 06 (Preset Single Register) is used to write a command to the slave unit.
6.5.
Exception Responses and Exception Codes
In a normal exchange, the master device sends a query to the Gassonic Observer-i. The Gassonic
Observer-i receives the query and returns a normal response to the master. If a communication error
occurs, there are three possible responses from the Gassonic Observer-i:
1. If the Gassonic Observer-i does not recognize the query due to communication error, no response
is returned from the Gassonic Observer-i and the master device will eventually process a timeout
condition for the query.
2. If the Gassonic Observer-i receives the query but detects a communication error (CRC, etc.), no
response is returned from the Gassonic Observer-i, and the master device will eventually process
a timeout for the query.
3. An exception code is returned when the Gassonic Observer-i receives the query without a
communication error, but cannot process it due to reading or writing to a non-existent or Illegal
Function Code, Illegal Command Starting Address or Register Address, or Illegal Data Value. The
exception response message has two fields that differentiate it from a normal response. See the
next section for more information.
Содержание Observer-i
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Страница 51: ...GASSONIC OBSERVER i 51 Figure 9 Calibration Routine ...