AERCO Modbus Communications Manual - Manual (Page 10)

GF-114
MODBUS
Communication
Chapter 1
OMM-0035_0C USER MANUAL Introduction & Description
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or EMS) matches the appropriate Baud Rate supported by the Network Slaves (BMS/BMS
II/ACS or C-More Controllers). Also, ensure that the Modbus Master can refresh the control
information to all C-More Slaves before the Heartbeat Timeout period expires.
1.4 MODBUS FUNCTION SET SUPPORT
The complete Modbus protocol includes a total of 24 Function Codes. However, for AERCO
BMS/BMS II/ACS and C-More Boiler Controllers, only the Codes listed in Table 1-2 are
supported. The supported Diagnostic Sub-Function Codes associated with Diagnostic Function
Code 08 are listed in Table 1-3.
Table 1-2: Required Function Code Set
Function Code Function Name
03
Read Holding Register (Read Multiple
Registers)
04 Read Input Registers
06 Preset (Write) Single Register
08
Diagnostics
(See Table 1-3 for supported Sub-Function
Codes)
17 Report Slave ID
Table 1-3: Minimum Diagnostic (Function Code 08) Sub-Function Set
Sub-
Function
Code
Sub-Function Name Comments
00 Return Query Data Loop-Back
01 Restart Communications Options Resets the Slave. Cancels Listen Only Mode.
02 Return Diagnostic Register Not Used
04 Force Listen Only Mode Reset by Restart Communications Option
10 Clear Counters and Diagnostic Register Also cleared at power up. Clears only the
counters
12 Return Bus Communication Error Count Slave CRC errors only.
13 Return Bus Exception Error Count Slave Exception Response count.
14 Return Slave Message Count
Number of messages addressed to the slave
and successfully processed. Includes
broadcast messages.
15 Return Slave No Response Count
Number of messages addressed to the slave
for which no response was returned.
18 Return Bus Character Overrun Count Number of overrun and framing errors.