Omron NX-AD series, User Manual

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5 I/O Refreshing
NX-series Analog I/O Units User’s Manual for Analog Input Units and Analog Output Units (W522)
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2 I/O Refres
hing
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2-4 F
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Run Refr
eshing
z Inputs
• The Analog Input Units repeatedly perform AD conversion in the order of inputs for which the used
channels are set to enable. AD conversion is not synchronized with I/O refreshing of the NX bus.
• At the time of I/O refreshing, the CPU Unit reads the converted values from the NX Unit for one
Unit that AD conversion is complete before the timing to read inputs.
z Outputs
• The Analog Output Units repeatedly perform DA conversion in the order of outputs for which the
used channels are set to enable. The outputs are refreshed once per DA conversion cycle for one
Unit when DA conversion of the last output is complete. The refreshing is not synchronized with
I/O refreshing of the NX bus.
• At the time of I/O refreshing, the Analog Output Units perform DA conversion with the refreshed
output set values from the outputs before the start of conversion.
I/O refreshing
of the NX bus
Analog Input Unit A
Analog Input Unit B
Timing to read inputs for each Unit is not simultaneous.
Timing to read
inputs
Input 1 Input 2 Input 3 Input 4 Input 1 Input 2 Input 3 Input 4 Input 1 Input 2 Input 3 Input 4 Input 1 Input 2 Input 3 Input 4 Input 3 Input 4
Input 4 Input 1 Input 2 Input 4 Input 1 Input 2 Input 4 Input 1 Input 2 Input 4
(c)
(b)
(d) Interval of the timing to read inputs is not constant.
(a) I/O refreshing for NX Units
Input refreshing Output refreshing
Analog Output Unit A
Analog Output Unit B
Output 1 Output 2 Output 3 Output 4 Output 1 Output 2 Output 3 Output 4 Output 1 Output 2 Output 3 Output 4 Output 1 Output 2 Output 3 Output 4
Timing to refresh outputs for each Unit is not simultaneous.
Refresh the output set
values by output refreshing
Output 1 Output 2 Output 3 Output 4 Output 2 Output 3 Output 4 Output 1 Output 4
Output 1: Previous output set values
Output 2 to 4: Current output set values
Output 1 to 4:
Previous output
set values Output 1 to 4:
Current output
set values Output 1 to 2:
Previous output
set values
Output 3 to 4:
Current output
set values
Output 1 to 4:
Current output
set values
Output 1 to 4:
Current output
set values
I/O refreshing
of the NX bus
(c)
(b)
(d) Interval of the timing to refresh outputs is not constant.
(a) I/O refreshing for NX Units
Input refreshing Output refreshing