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Basic I/O Unit Instructions Section 3-22
Flags
Precautions When “0001” is designated for the number of words to be transferred (D+1),
the data for S can be designated by a constant. If a constant is designated for
S when the number of words to be transferred is not “0001,” an error will occur
and the Error Flag will turn ON.
The Equals Flag will turn ON if the writing operation is completed normally.
The Equals Flag will turn OFF if the writing operation cannot be completed
normally due to the Special I/O Unit or CPU Bus Unit being busy.
Whenever any of the following occur, an error will occur and the Error Flag will
turn ON.
• There is an I/O Unit verification error, a Special I/O Unit setting error, a
Special I/O Unit setting error, or a Special I/O Unit error at the Special I/O
Unit.
• There is an I/O Unit verification error, a CPU Bus Unit setting error, a CPU
Bus Unit setting error, or a CPU Bus Unit error at the CPU Bus Unit.
• The number of words to transfer (D) is outside the range of 0001 to 0080
(hex).
• The unit number (D) is outside the range of 0000 to 005F hex or 8000 to
800F hex.
• A Special I/O Unit or CPU Bus Unit not affected by IOWR(223) is desig-
nated.
• A Special I/O Unit with a setting error or an error is designated.
• A CPU Bus Unit with a setting error or an error is designated.
When IOWR(223) 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 IOWR(223) instruction.
If the Special I/O Unit or CPU Bus Unit is busy, the writing operation will not be
executed. Use the Equals Flag to create a self-maintaining program, as
shown below, so that IOWR(223) will be executed with each cycle until the
writing operation is executed.
Name Label Operation
Error Flag ER ON if the number of words to transfer (D) is outside the
range of 0001 to 0080 hex.
ON if the unit number (D) is outside the range of 0000 to
005F hex or 8000 to 800F hex.
ON if S is designated by a constant when the number of
words to be transferred (D+1) is not 0001 hex.
ON if a Special I/O Unit or CPU Bus Unit not affected by
IOWR(223) is designated.
ON if a Special I/O Unit with a setting error or an error is
designated.
ON if a CPU Bus Unit with a setting error or an error is
designated.
OFF in all other cases.
Equals Flag = ON if writing operation is completed normally.
OFF if writing operation is not completed normally.
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