Modbus Rtu - Control Techniques Commander SE Advanced User's Manual

decimal, so this is the final BCC value. 53 decimal is the ASCII character '5'.
The drive should reply with ACK control character if the message was received correctly, and the BCC agrees with the drive
calculation.
1.3.3 Re-writing data
Once a complete 'write' message has been sent to a drive, and the drive has responded with either a 'ACK' or 'NAK'
character, subsequent 'write' messages to that particular drive can use a re-write message structure. The address does not
need to be re-transmitted. The 're-write' message structure is as follows:
CC
STX M1
When a different drive needs to be addressed, or an ACK or NAK response is not received from the current drive addressed,
the 're-write' facility can no longer be used.
the correct address, etc.
1.4

Modbus RTU

1.4.1 Parameters
11.24 Serial Communication Mode
Range
0 ~ 2
0 AnSI
1 rtu
2 F.bus
To implement Modbus RTU, parameter 11.24 should be set to 1
11.25 Data (baud) rate
Range
0 ~ 3
0 2.4
1 4.8
2 9.6
3 19.2
Used to select the communications port data (baud) rate.
11.23 Modbus node address
Range
0.1 ~ 24.7
Used to define the network node address for the Commander SE. All nodes on a Modbus network MUST be configured with
a unique node address.
1.4.2 Modbus frame specification
1 start bit
The COMMANDER SE does not use the parity bit.
1.4.3 Modbus register value
All Commander SE parameters are mapped to the 4XXXX series of Modbus registers. To convert from a parameter number
to a Modbus register, remove the decimal point from the parameter number e.g. parameter 11.22 = register 41122. All
parameters (including bit parameters) are handled as signed 16 bit values.
1.4.4 Supported functions
0x03 (3)
0x10 (16)
0x17 (23)
When using multiple write or read commands, the parameters written to or read from must be consecutive. If a block of
parameters is written to or read from where there is a missing parameter, the slave will respond with an exception code.
Therefore this block should be split into a number of smaller blocks so as not to write to or read from a missing parameter.
The maximum number of consecutive parameters that can be written to or read from is 16.
1.4.5 Broadcast messages
Commander SE also supports broadcast messages. If the master controller sends a WRITE message to node address 0, all
nodes will accept the message but none will reply to the master.
14
Parameter
M2 P1 P2 D1
The particular drive can only be addressed by using the full 'write' message with
Default Type Limitations
0 (AnSi) RW
Ansi protocol half duplex serial communications 2 wire
Modbus RTU high data rate protocol
Fieldbus communications mode
Default Type Limitations
1 (4.8) RW
2,400 bits/sec
4,800 bits/sec
9,600 bits/sec
19,200 bits/sec
Default Type Limitations
1.1 RW
8 data bits 1 stop bit
Read holding registers Read Multiple Parameters
Preset multiple registers Write Multiple Parameters
Read/Write registers Read and Write Multiple Parameters
Data CC
D2 .... Dn ETX
Level 2 parameter
P 41
Level 2 parameter
P 42
Level 2 parameter
P 43
BCC
BCC
Commander SE Advanced User Guide
Issue Number: 4