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Diagnostics Optimization CT MODBUS RTU Technical Data
408 E300 Design Guide
Issue Number: 1
The core drive always uses the Modbus rtu protocol and is always a slave. Serial Mode (M02) defines the data format used by the serial comms
interface. The bits in the value of Serial Mode (M02) define the data format as follows. Bit 3 is always 0 in the core product as 8 data bits are required
for Modbus rtu.
Bit 2 selects either standard or modified register mode. The menu and parameter numbers are derived for each mode as given in the table below.
Standard mode is compatible with Unidrive SP. Modified mode is provided to allow register numbers up to 255 to be addressed. If any menus with
numbers above 63 should contain more than 99 parameters, then these parameters cannot be accessed via Modbus rtu.
Changing the parameters does not immediately change the serial communications settings. See Reset Serial Communications (M06) for more
details.
Serial Baud Rate (M03) defines the baud rate used by the serial comms interface.
Changing the parameters does not immediately change the serial communications settings. See Reset Serial Communications (M06) for more
details.
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.
Bits 3 2 1 and 0
Format
Number of data bits
0 = 8 bits
1 = 7 bits
Register mode
0 = Standard
1 = Modified
Stop bits and Parity
0 = 2 stop bits, no parity
1 = 1 stop bit, no parity
2 = 1 stop bit, even parity
3 = 1 stop bit, odd parity
Register mode Register address
Standard (mm x 100) + ppp - 1 where mm ≤ 162 and ppp ≤ 99
Modified (mm x 256) + ppp - 1 where mm ≤ 63 and ppp ≤ 255
M03 Serial Baud Rate
Mode Open-Loop, RFC-A, RFC-S
Minimum 0 Maximum 10
Default 6 Units
Type 8 Bit User Save Update Rate Read on serial communications reset
Display Format Standard Decimal Places 0
Coding RW, Txt
Value Text
0 300
1 600
2 1200
3 2400
4 4800
5 9600
6 19200
7 38400
8 57600
9 76800
10 115200
M04 Minimum Comms Transmit Delay
Mode Open-Loop, RFC-A, RFC-S
Minimum 0 Maximum 250
Default 2 Units ms
Type 8 Bit User Save Update Rate Read on serial communications reset
Display Format Standard Decimal Places 0
Coding RW, BU
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