Communication
54
Exception codes
The RETA-01 supports the Modbus exception codes shown
below.
Table 13. Supported exception codes
Function codes
The RETA-01 supports the Modbus function codes shown below.
Table 14. Supported function codes
Exception
code
Name Description
01 Illegal func-
tion
Unsupported command
02 Illegal data
address
Address does not exist or is read/write-pro-
tected
03 Illegal data
value
Value is outside minimum and maximum
limits. Parameter is read-only
Function
code
Name Description Modbus
class
03 Read hold-
ing registers
Reads the binary contents of the
holding registers (4X references)
in the slave.
0
06 Preset sin-
gle register
Presets a value into a single hold-
ing register (4X reference).
1
16 (10h) Preset multi-
ple registers
Presets values into a sequence of
holding registers (4X references).
0
23 (17h) Read/Write
registers
Performs a combination of one
read and one write operation in a
single Modbus transaction. The
function first reads a group of
4XXXX registers and then writes
new contents to a another group
of 4XXXX registers.
2