3-2-19 External I/O Response Cycle On The Overall System - Omron SYSMAC CS Series Operation Manual

Description of Operation
Note

3-2-19 External I/O Response Cycle on the Overall System

1,2,3...
Example
Note
Maximum External I/O Response Time
CS1W-LCB01 and CS1W-
LCB05 Loop Control
Boards and Loop-control
CPU Units (CJ1G-
CPU@@P)
132
The LCB@@s do not support the automatic operation cycle switching function
of the Loop Control Units. The High Load Alarm Flag (A42408), however, will
turn ON if the LCB load rate exceeds 80% for 6 seconds. If this bit turns ON,
use longer operation cycles or add Loop Control Units to distribute process-
ing.
The Loop Controller exchanges field I/O values (analog input values, analog
output values, contact inputs and contact outputs) with external Units by the
following method.
1. The Analog Input/Output Unit or the Basic I/O Unit refresh the I/O memory
on the CPU Unit.
2. The Loop Controller exchanges data allocated to I/O memory on the CPU
Unit according to the operation cycle of each function block.
Data exchange of analog input, PID operation and analog output
Analog Input Unit
A/D
Log input
conversion
I/O refreshing
Analog Output
Unit
D/A
Log input
conversion
I/O refreshing
The external I/O response time in the overall system (simply called "the exter-
nal I/O response time" from here on) refers to the time from when the analog
input data is converted and the Analog Input Unit reads the analog input value
to when the PID operation is performed and the Analog Output Unit outputs
analog output value. This response time indicates the response of the overall
system.
The external I/O response time is equivalent to twice the input sampling cycle
(or operation cycle) on a general controller. For this reason, when designing
the system, calculate the external I/O response time according to the formu-
lae shown below, and study whether or not there will be any problem with con-
trol with the target application. In particular, study whether or not there will be
any problem in controllability of PID control in the case of fast-response con-
trol targets, such as pressure or flowrate. Calculate the external I/O response
time using the methods described in the following sections.
The maximum external I/O response time is calculated as follows:
2 x A/D conversion time + (2 x CY) + (2 x T) + 2 x D/A conversion time
where,
CY: Cycle time of the CPU Unit
T: Operation cycle
Loop Controller
CPU Unit
Function block
I/O memory
Analog
Analog Input
input
block
Operation
converted
cycle
value
PID block
I/O memory
Analog output
Analog
block
input
Operation
converted
cycle
value
Section 3-2
Execution
cycle 0.2 s
Execution
cycle 0.2 s
Execution
cycle 0.2 s