LDU 179.1 Technical Manual rev. 1.10 - February 2019 Page 35 of 45
8.8.
Commands for External I/O Control
– IN, IO and OM
8.8.1. IN
Read status of the logic inputs
[ SDO 2100 sub 07 ]
This command reads the status of the logic inputs.
Master (PC / SPS) sends
Slave (LDU 179.1) responds
Meaning
IN
IN:0000
Input 0 and 1 inactive
IN
IN:0001
Input 0 active
IN
IN:0010
Input 1 active
The status response is in the form of a four digit code where 0 = false and 1 = t
rue (inputs are active ‘high’).
The least significant bit corresponds to Input 0.
8.8.2. IO
Read / modify the status of the logic outputs
[ SDO 2100 sub 06 ]
This command reads and can modify the status of the logic outputs (if enabled by the OM command). The
status response is in the form of a four digit code where 0 = false and 1 = true (outputs are normally open, open
drain MOSFET’s), the least significant bit corresponds to Output 0.
Master (PC / SPS) sends
Slave (LDU 179.1) responds
Meaning
IO
IO:0001
Output 0 is active
IO
IO:0010
Output 1 is active
The status of the outputs can be changed by issuing the IO command with the appropriate 4 digit code e.g.
IO 0001 where in this example output 0 will be activated (FET conducting). Please note that the status of the
logic outputs is normally determined by the internal setpoints (see section 10.9.2) and therefore setting the
logic output status using the IO commands is
not
allowed.
Setting
Master (PC / SPS) sends
Slave (LDU 179.1) responds
Meaning
IO_0010
OK
Set output 1 active
IO_0011
OK
Set outputs 0 and 1 active
However, the OM command can be used to allow the status of the logic outputs to be set via the IO
command.
8.8.3. OM Control of the logic outputs by the host application
[ SDO 2100 sub 0C ]
The logic outputs can be controlled by the host application (as opposed to the normal internal setpoints) if
they are enabled by the OM command and the appropriate 4 digit code.
Master (PC / SPS) sends
Slave (LDU 179.1) responds
Meaning
OM
OM:0001
Setting Output 0 is enabled
OM
OM:0011
Setting Outputs 0 and 1 are enabled
A “1” bit in the code enables the corresponding logic output to be controlled by the host application using
the IO command. A “0” in the code leaves the corresponding logic output controlled by the internal setpoint.
Logic output 0 is again the least significant bit.
Setting
Master (PC / SPS) sends
Slave (DAD 179.1) responds
Meaning
OM_0010
OK
Enables output 1
OM_ 0011
OK
Enables outputs 0 and 1
Note:
When reading the status of the logic outputs using the IO command, the setpoint status will be
returned regardless of the OM setting. Sending OM_0000 disables the external logic output control.
