298 Fieldbus control with the embedded fieldbus
Modbus mapping
The following Modbus function codes are supported by the drive.
Function
Code
Hex (dec)
Additional information
Read Coil
Status
01 (01)
Reads discrete output status. The individual bits of the control word
are mapped to coils 1...16. Relay outputs are mapped sequentially
beginning with Coil 33 (eg, RO1 = Coil 33).
Read Discrete
Input Status
02 (02)
Reads discrete input status. The individual bits of the status word
are mapped to inputs 1...16 or 1...32, depending on the active
profile. Terminal inputs are mapped sequentially beginning with
input 33 (eg, DI1 = Input 33).
Read Multiple
Holding
Registers
03 (03)
Reads the contents of registers in a slave device.
Parameter sets, control, status and reference values are mapped
as holding registers.
Read Multiple
Input
Registers
04 (04)
Reads multiple input registers. The 2 analog input channels are
mapped as input registers 1 and 2.
Force Single
Coil
05 (05)
Writes a single discrete output. The individual bits of the control
word are mapped to Coils 1...16. Relay outputs are mapped
sequentially beginning with Coil 33 (eg, RO1 = Coil 33).
Write Single
Holding
Register
06 (06)
Writes to a single register in a slave device.
Parameter sets, control, status and reference values are mapped
as holding registers.
Diagnostics
08 (08)
Provides a series of tests for checking the communication between
the master and the slave devices, or for checking various internal
error conditions within the slave.
The following subcodes are supported:
00 Return Query Data: The data passed in the request data field is
to be returned in the response. The entire response message
should be identical to the request.
01 Restart Communications Option: The slave device serial line
port must be initialized and restarted, and all of its communication
event counters cleared. If the port is currently in Listen Only Mode,
no response is returned. If the port is not currently in Listen Only
Mode, a normal response is returned before the restart.
04 Force Listen Only Mode: Forces the addressed slave device to
Listen Only Mode. This isolates it from the other devices on the
network, allowing them to continue communicating without
interruption from the addressed remote device. No response is
returned. The only function that is processed after this mode is
entered is the Restart Communications Option function (subcode
01).
Force Multiple
Coils
0F (15)
Writes multiple discrete outputs. The individual bits of the control
word are mapped to Coils 1...16. Relay outputs are mapped
sequentially beginning with Coil 33 (eg, RO1 = Coil 33).
Write Multiple
Holding
Registers
10 (16)
Writes to the registers (1 to approximately 120 registers) in a slave
device.
Parameter sets, control, status and reference values are mapped
as holding registers.
Read/Write
Multiple
Holding
Registers
17 (23)
Performs a combination of one read operation and one write
operation (function codes 03 and 10) in a single Modbus
transaction. The write operation is performed before the read
operation.
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