420 Fieldbus control through the embedded fieldbus interface (EFB)
Modbus function codes
The table below shows the Modbus function codes supported by the embedded
fieldbus interface.
Code
Function name
Description
01h
Read Coils
Reads the 0/1 status of coils (0X references).
02h
Read Discrete Inputs
Reads the 0/1 status of discrete inputs (1X
references).
03h
Read Holding Registers
Reads the binary contents of holding registers (4X
references).
05h
Write Single Coil
Forces a single coil (0X reference) to 0 or 1.
06h
Write Single Register
Writes a single holding register (4X reference).
08h
Diagnostics
Provides a series of tests for checking the
communication, or for checking various internal error
conditions.
Supported subcodes:
• 00h Return Query Data: Echo/loopback test.
• 01h Restart Comm Option: Restarts and initializes
the EFB, clears communications event counters.
• 04h Force Listen Only Mode
• 0Ah Clear Counters and Diagnostic Register
• 0Bh Return Bus Message Count
• 0Ch Return Bus Comm. Error Count
• 0Dh Return Bus Exception Error Count
• 0Eh Return Slave Message Count
• 0Fh Return Slave No Response Count
• 10h Return Slave NAK (negative acknowledge)
Count
• 11h Return Slave Busy Count
• 12h Return Bus Character Overrun Count
• 14h Clear Overrun Counter and Flag
0Bh
Get Comm Event
Counter
Returns a status word and an event count.
0Fh
Write Multiple Coils
Forces a sequence of coils (0X references) to 0 or 1.
10h
Write Multiple Registers
Writes the contents of a contiguous block of holding
registers (4X references).
16h
Mask Write Register
Modifies the contents of a 4X register using a
combination of an AND mask, an OR mask, and the
register’s current contents.
17h
Read/Write Multiple
Registers
Writes the contents of a contiguous block of 4X
registers, then reads the contents of another group of
registers (the same or different than those written) in
a server device.
ACS580 FW.book Page 420 Wednesday, September 21, 2016 9:48 PM
