Control Techniques Digitax ST Advanced User's Manual page 146

Parameter
Menu 11
structure
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
• Maximum number of 16 bit registers that can be written to, or read from, a Solutions Module or via a Solutions Module - see Solutions Module
User Guide
• The communications buffer can hold a maximum of 128bytes
Modbus RTU protocol, but with SM-Keypad Plus only
This setting is used for disabling comms access when the SM-Keypad Plus is used as a hardware key. See the SM-Keypad Plus User Guide for more
information.
11.25 Baud rate
Bit SP
Coding
Range 0 to 9
Default 6
Update rate Background read
Used in all comms modes to define the baud rate.
Parameter value String/baud rate
0
1
2
3
4
5
6 19200
7 38400
8* 57600
9* 115200
*Modbus RTU only
This parameter can be changed via the drive keypad, via a Solutions Module or via the comms interface itself. If it is changed via the comms
interface, the response to the command uses the original baud rate. The master should wait at least 20ms before sending a new message using the
new baud rate.
11.26 Minimum comms transmit delay
Bit SP
Coding
Range 0 to 250 ms
Default 2
Update rate Background read
There will always be a finite delay between the end of a message from the host (master) and the time at which the host is ready to receive the
response from the drive (slave). The drive does not respond until at least 1ms after the message has been received from the host allowing 1ms for the
host to change from transmit to receive mode. This initial delay can be extended using Pr 11.26 if required for both ANSI and Modbus RTU protocols.
Pr 11.26
The transmit buffers are turned on and data transmission begins immediately after the
0
initial delay (≥ 1ms)
The transmit buffers are turned on after the initial delay (≥ 1ms) and data transmission
1
begins after 1ms.
The transmit buffers are turned on after the initial delay (≥ 1ms) a delay of at least the
2 or more
time specified in Pr 11.26 and data transmission begins 1ms later.
Note that the drive holds its own transmitters active for up to 1ms after it has transmitted data before switching to the receive mode, the host should
not send any data during this time.
Modbus RTU uses a silent period detection system to detect the end of a message. This silent period is either the length of time for 3.5 characters at
the present baud rate or the length of time set in Pr 11.26, whichever is the longest.
146
Keypad and
Parameter x.00
display
FI DE Txt VM DP ND
1
300
600
1200
2400
4800
9600
FI DE Txt VM DP ND
Action
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Parameter Advanced parameter
description format descriptions
RA NC NV PT US RW BU
1 1
RA NC NV PT US RW BU
1 1
Serial comms Electronic
protocol nameplate
PS
1
PS
1
Digitax ST Advanced User Guide
Issue Number: 1
Performance