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Diagnostics Optimization CT MODBUS RTU Technical Data
E300 Design Guide 121
Issue Number: 1
Minimum Comms Transmit Delay (M04)
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 Minimum Comms Transmit Delay (M04) if required.
The drive holds its own transmitters active for up to 1 ms after it has transmitted data before switching to the receive mode; the host should not send
any data during this time.
Changing the parameters does not immediately change the serial communications settings See note below for more details.
Silent Period (M05)
The silent period defines the idle time required to detect the end of a received data message. If Silent Period (M05) = 0 then the silent period is at
least 3.5 characters at the selected baud rate. This is the standard silent period for MODBUS RTU. If Silent Period (M05) is non-zero it defines the
minimum silent period in milliseconds.
Changing the parameters does not immediately change the serial communications settings. See note below for more details.
When Serial Address (M01), Serial Mode (M02), Serial Baud Rate (M03), Minimum Comms Transmit Delay (M04) or Silent Period (M05) are modified
the changes do not have an immediate effect on the serial communications system. The new values are used after the next power-up or if Reset
Serial Communications (M06) is set to one. Reset Serial Communications (M06) is automatically cleared to zero after the communications system is
updated.
This does not save any changes made and a separate parameter save is required.
Value Action
0
The transmitters are turned on and data transmission
begins immediately after the initial delay (≥1 ms)
1
The transmitters are turned on after the initial delay (≥1
ms) and data transmission begins 1ms later
2 or more
The transmitters are turned on after a delay of at least
the time specified by Minimum Comms Transmit Delay
(M04) and data transmission begins 1ms later
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