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LDU 68 Series Manual
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5.11 Communication setup Commands – AD, CL, BR, DX, OP, TD
NOTE: These settings will only take effect after a power on reset (remember to store the settings
using the WP command before turning the power off)
With this command, the following Baud rates can be set up: 9600, 19200, 38400, 5760 and 115200
baud.
With this command the communication can be set to half (DX=0) or full (DX=1) duplex.
Factory default: 9600 Baud
Refer to section 2 (page 4) for details of how to carry out an automatic adjustment of the baud rate
Half duplex communication can be used for 2 wire RS485 communication. The auto transmit
commands SG and SF will only work if full duplex (DX=1) is selected. Factory default DX=0
Request / Set device address
Setting the device address to 0 will cause the device to be permanently active, listening and
responding to every command on the bus without the need for an OP command.
Factory default: Address 0
Refer to section 2 (page 4) for details of how to carry out a manual setting of the address by
soldering SW3.
AD Device address setup / request
Master (PC / PLC) sends
LDU XX.X responds
Result
AD
AD_49
A:000
OK
Address set to 0
Address changed to 49
Master (PC / PLC) sends
LDU XX.X responds
Result
BR
BR_115200
B:9600
OK
Baud rate set to 9600
Baud rate changed to 115K2 baud
Master (PC / PLC) sends
LDU XX.X responds
Result
DX
DX_1
X:000
OK
Half duplex set
Communication changed to full duplex
CL Close Device address n
BR Request / Setup Baud Rate
DX Half or full duplex communication
Master (PC / PLC) sends
LDU XX.X responds
Result
CL_3
OK
Device 3 closed
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Request / Enable device communication
This command, if sent without parameters, requests the address or device number of the device
active on the bus. If sent with parameters, this enables the device defined by the parameters.
OP Device communication enable / request
The requested device acknowledges its readiness and responds to all bus commands until a
further OP command arrives with a different device address or a CL command is received.
Master (PC / PLC) sends
LDU XX.X responds
Result
OP
OP_14
O:0003
OK
Device 3 open
Device 14 opened
This command allows to set a delay between the LDU receiving a command and responding. You
can set this delay anywhere between 0 and 255 milliseconds.
To read the current Time Delay setting issue the TD command without any parameters. To change
the value of Time Delay issue the TD command followed by a space and then the value of the
delay required in milliseconds e.g. TD 255 to set the delay to 255 milliseconds.
To save the new Time Delay setting, issue the WP command.
TD Transmit Delay
This command is particularly useful when LDUs are used on a 2 wire RS485 bus where the host
PLC is unable to ‘turn around’ the transmit and receive lines quick enough to prevent missing part
or all of the answer.
Request / Set Transmit Delay time
Master (PC / PLC) sends
LDU XX.X responds
Result
TD
TD_1
D:0000
OK
Transmit delay set to 0 milliseconds
Transmit delay changed to 1 millisecond
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