Ct Modbus Rtu Specification; Short Commands - Control Techniques unidrive sp Advanced User's Manual

Parameter Keypad and Parameter
structure display
The drive only acts on messages received that contain a drive address if
the whole drive address or drive group address match the whole
address or the group address in the message, or if the address in the
message is 0 (i.e. a global message). Global or group addressing allows
data to be written to more than one drive with one command. The drive
does not give a response to a global or group write message. Although it
is possible to perform a global or group read, this would result in
messages crashing if more than one drive responds to the command.
Message
Drive address
address
7.8 7.8
7.8 7.8
7.8 7.0
7.8 7.0
7.8 0.0
7.8 0.0
7.1.6

Short commands

The following short commands can be used:
NAK Not acknowledge (Ctl U)
This is the same as requesting the value of the last parameter to be read
or written to. The response is the same as for a normal read.
ACK Acknowledge (Ctl F)
This is the same as requesting the value of the parameter after the last
parameter to be read or written to. The response is the same as for a
normal read.
BS Back space (Ctl H)
This is the same as requesting the value of the parameter before the last
parameter to be read or written to. The response is the same as for a
normal read.
STX Start of text (Ctl B)
st
M1
Menu number: 1
nd
M2
Menu number: 2
P1
Parameter number: 1
P2
Parameter number: 2
st
D1
Data: 1 digit
nd
D2
Data: 2 digit
-
-
Dn Data: nth digit
ETX End of text (Ctl C)
Checksum
Writes to the specified parameter at the same drive address as used by
the last read or write.
All the short commands will only read from the drive or write to the drive
if a valid address has already been sent to the drive in a previous
command. The address is registered as being valid once a read or write
command has been completed provide the address was valid for the
drive even if the parameter does not exist. The valid address is
cancelled if a message is received for a non-valid address or one of the
following occurs:
1. The command is aborted because a non-numerical value is received
in the drive address, menu or parameter numbers.
Unidrive SP Advanced User Guide
Issue Number: 7
Parameter Advanced parameter
x.00 description format descriptions
Command Action
Read Read
Write Write
Read Read
Write with no
Write
response
Read Read
Write with no
Write
reponse
digit
digit
st
digit
nd
digit
www.controltechniques.com
http://nicontrols.com
Serial comms
Macros
protocol
2. The command is aborted because the two digits for drive address 1
nd
digit, drive address 2 digit, menu number or parameter number are
not the same as each other.
3. EOT is received.
4. A character other than NAK, ACK, BS or STX is sent as a short
command.
5. A character other than ENQ is sent at the end of a read command.
7.1.7 Summary of control characters
STX Start of text
ETX End of text
EOT End of transmission
ENQ Enquiry
ACK Acknowledge
BS Back space
NAK Not acknowledge
7.2

CT Modbus RTU specification

This section describes the adaptation of the MODBUS RTU protocol
offered on Control Techniques' products. The portable software class
which implements this protocol is also defined.
MODBUS RTU is a master slave system with half-duplex message
exchange. The Control Techniques (CT) implementation supports the
core function codes to read and write registers. A scheme to map
between MODBUS registers and CT parameters is defined. The CT
implementation also defines a 32bit extension to the standard 16bit
register data format.
The CMP protocol is also supported using a vendor specific function
code. The CMP protocol is provided on some CT products for program
download, program debug, advanced diagnostics, etc.
Parameter
Database
#x.y
MODBUS RTU
RTU framing
Physical layer
Electronic Feature look-
Performance
nameplate up table
ASCII code Ctl code
02
03
04
05
06
08
15
CMP
UART
st
B
C
D
E
F
H
U
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