Omron CS1G/H-CPUxxH Instructions Manual page 854

Basic I/O Unit Instructions
• The designated Special I/O Unit is on SYSMAC BUS.
• A Special I/O Unit not affected by IORD(222) is designated.
• A Special I/O Unit with a Special I/O Unit setting error or a Special I/O
Unit error is designated.
When IORD(222) is executed, the execution results are reflected in the condi-
tion flags. In particular, the Equals Flag turns ON when reading is completed.
Input the condition flags such as the Equals Flag with output branching from
the same input conditions as the IORD(222) instruction.
If the Special I/O Unit is busy, the reading operation will not be executed. Use
the Equals Flag to create a self-maintaining program, as shown below, so that
IORD(222) will be executed with each cycle until the reading operation is exe-
cuted.
When the input condition is met, self maintenance is performed by output A
and IORD(222) is executed with each cycle until the Equals Flag turns ON.
When the reading is completed and the Equals Flag turns ON, output B turns
ON and the self maintenance is cleared.
Be sure to place condition flags directly after IORD(222) instructions, and not
after any other instructions. If a condition flag is placed after another instruc-
tion, it will be affected by the execution results of that instruction.
B
=
A
Section 3-23
IORD
C
S
D
B
A
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