Menu 11 Introduction
Parameter
x.00
Parameter
description format
Keypad and
display
Serial
communications
CT Modbus
RTU
PLC Ladder
programming
CTSoft Menu 0
Advanced parameter
descriptions
140 Commander SK Advanced User Guide
www.controltechniques.com Issue Number: 9
Address 0 is used to globally address all slaves, and so this address should not be set in this parameter.
The communications port on the Commander SK will support Modbus RTU protocol only. Full details of the CT implementation of Modbus RTU are
given in "CT MODBUS RTU specification".
The protocol provides the following facilities:
• Drive parameter access with basic Modbus RTU
• Drive parameter database upload via CMP extensions
The following product specific limitations apply:
• Maximum slave response time when accessing the drive is 100ms
• Maximum number of 16 bit registers that can be written to, or read from, the drive itself is limited to 16
• The communications buffer can hold a maximum of 128 bytes
Modes 0, 1 and 4 are for Modbus slave mode. Modes 2 and 3 allow a drive user program to control the comms.
0: mode 0 8 data bits and 1 stop bit with no parity (Commander SE backward compatibility)
1: mode 1 8 data bits and 2 stop bits with no parity
2: mode 2 7 data bits and 1 stop bit with even parity
3: mode 3 8 data bits and 2 stop bits with no parity
4: mode 4 8 data bits and 1 stop bit with even parity
This parameter is used to select the comms port baud rate in kilo baud.
Modbus RTU uses a silent period detection system to detect the end of a message. This silent period is normally the length of time for 3.5 characters
at the present baud rate, but for systems that cannot turn the communications buffers around fast enough this time can be extended to the time
programmed in Pr 11.26.
This parameter is used to automatically set up the user programmable area in the level 3 parameter set according to the required drive configuration.
Other default parameters may also be changed automatically by the drive configuration. See Table 10-23 for drive configuration parameter changes.
A change to Pr 11.27 is set on the exit of parameter edit mode or on a drive reset. The drive must be disabled, stopped or tripped for a change to take
place. If Pr 11.27 is changed while the drive is running, the parameter will return to its pre-altered value. Following a drive configuration change, the
parameters are automatically stored in EEPROM.
In all of the following settings, the status relay is set up as a drive ok relay.
11.24 Modbus RTU / user serial mode
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
111
Range 0 to 3
Default 1
Update rate Background
11.25 Serial comms baud rate {43}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
1 111
Range 2.4(0), 4.8(1), 9.6(2), 19.2(3), 38.4(4),
Default 19.2(3)
Update rate Background
11.26 Silent period extension
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
111
Range 0 to 250 ms
Default 2
Update rate Background
11.27 Drive configuration {05}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
1 1111
Range AI.AV(0), AV.Pr(1), AI.Pr(2), Pr(3), PAd(4), E.Pot(5), tor(6), Pid(7), HVAC(8)
Default Eur: AI.AV(0), USA: PAd(4)
Update rate Actioned on exit of edit mode or drive reset.
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