MITSUBISHI ELECTRIC 700 Series - Manual (Page 74)

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I/O Processing Method
3
SEQUENCE PRO
G
RAM
M
ING
3.6 I/O Processing Method
The control system is a refresh system.
3.6.1 What is refresh system?
In the refresh system, control input terminal changes are batch-imported into the input
data memory of the CPU before execution of each scan, and the data of this input data
memory are used as the input data for operation execution.
Each program operation result of the output (Y) is output to the output data memory,
and after the END instruction is executed, the contents of the output data memory are
batch-output from the control output terminal.
Fig 3.6 I/O Data Flows in Refresh System
• Input refresh
Before execution of step 0, input data are batch-read from the input module (1))
and stored into the input (X) data memory.
• Output refresh
Before execution of step 0, the data of the output (Y) data memory (2)) are batch-
output to the output module.
• When input contact instruction is executed
Input data are read from the input (X) data memory (3)) and the sequence
program is executed.
• When output contact instruction is executed
Output data are read from the output (Y) data memory (4)) and the sequence
program is executed.
• When output OUT instruction is executed
The operation result (5) of the sequence program is stored into the output (Y) data
memory.
CPU
(Central Processing Unit)
1)
2)
4)
5) Y20
Y22
X0
3) Input (X) data
memory
Output (Y)
data memory
Control input
terminal At input refresh
Control output
terminal At output refresh
PLC