MCD Modbus Module Instructions
AP ASCII Protocol
MG.17.F5.02 - VLT
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9
10.
AP ASCII Protocol
The message fragments used to communicate with the Modbus Module as an AP ASCII slave device
are shown below. The message fragments may be assembled into complete messages as described
in the sections that follow.
N.B.!:
Data must be transmitted in 8-bit ASCII, no parity, one stop bit.
Message Fragment Type ASCII Character String or
(Hexadecimal Character String)
Send address
EOT
(04h
[nn]
[nn]
[lrc]
[lrc]
ENQ or
05h)
Send command
STX
[ccc]
[lrc]
ETX or
Send request
(02h
[ccc]
[lrc]
03h)
Receive data
STX
(02h
[dddd]
[dddd]
[lrc]
[lrc]
ETX or
03h)
Receive status
STX
(02h
[ssss]
[ssss]
[lrc]
[lrc]
ETX or
03h)
ACK (acknowledge)
ACK
(06h)
or
NAK (negative
acknowledge)
NAK
(15h)
or
ERR (error)
BEL
(07h)
or
nn =
two byte ASCII number representing the soft starter address where each decimal digit is
represented by n.
lrc =
two byte longitudinal redundancy check in hexadecimal.
ccc =
three byte ASCII command number where each character is represented by c.
dddd =
four byte ASCII number representing the current or temperature data where each decimal digit is
represented by d.
ssss =
four byte ASCII number. The first two bytes are ASCII zero. The last two bytes represent the nibbles
of a single byte of status data in hexadecimal.
10.1.
Commands
Commands can be sent to the soft starter using the following format:
Send
address
ACK
Send
command
ACK
Possible error responses:
NAK (Invalid
LRC)
= Master
=
Slave
(soft starter)
Command
ASCII
Comment
Start
B10
Initiates a start
Stop
B12
Initiates a stop
Reset
B14
Resets a trip state
Quick stop
B16
Initiates an immediate removal of voltage from the motor. Any soft
stop settings are ignored.
Forced communication trip
B18
Causes a communications trip