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I/O Area Section 9-3
Normal I/O Refreshing The status of I/O points on external devices is read once each cycle after pro-
gram execution.
In the following example, CIO 000101 is allocated to switch 1, an external
switch connected to the input terminal of an Input Unit. The ON/OFF status of
switch 1 is reflected in CIO 000101 once each cycle.
Immediate Refreshing When the immediate refreshing variation of an instruction is specified by
inputting an exclamation point just before the instruction, and the instruction’s
operand is an input bit or word, the word containing the bit or the word itself
will be refreshed just before the instruction is executed. This immediate
refreshing is performed in addition to the normal I/O refreshing performed
once each cycle.
1,2,3... 1. Bit Operand
Just before the instruction is executed, the ON/OFF status of the 16 I/O
points allocated to the word containing the specified bit will be read to the
PLC.
2. Word Operand
Just before the instruction is executed, the ON/OFF status of the 16 I/O
points allocated to the specified word will be read to the PLC.
In the following example, CIO 000101 is allocated to switch 1, an external
switch connected to the input terminal of an Input Unit. The ON/OFF status of
switch 1 is read and reflected in CIO 000101 just before !LD 000101 is exe-
cuted.
LD 000101
000101
CIO 000101
Ladder symbol
Mnemonic
CPU Unit
Bit allocation
Once
each
cycle
Switch 1
Input Unit
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