I/O Read 2: Rd2(280) - Omron CVM1D Operation Manual

Special I/O Instructions

5-33-2 I/O READ 2: RD2(280)

Ladder Symbol
(280)
RD2
Description
Precautions
Flags
Operand Data Areas
C: Control word
C S D
S: Source word
D: First destination word
When the execution condition is OFF, RD2(280) is not executed. When the ex-
ecution condition is ON, RD2(280) reads the memory contents of a Special I/O
Unit to specified words (beginning with D) in the Programmable Controller
through the source word ( S). The word specified for S is the third of the four
words (i.e., the first input word) that serve as the interface with the Special I/O
Unit.
The words that are to be transferred are specified by the control word. The con-
tents of the control word are as follows:
Control Word Contents
MSB
The beginning address to be read specifies the rightmost (lowest) word of the
range of data that is to be read from the memory area in the Special I/O Unit.
If 00 is specified as the number of words to be read, the instruction will not be
executed. If the sum of the beginning address to be read plus the number of
words to be read is more than 100 (binary), the Error Flag (A5003) will turn ON.
If an error occurs at the Special I/O Unit (such as, for example, a non-readable
area being specified), the Carry Flag (A50004) will turn ON.
The Equals Flag (A50006) can be used to check whether or not RD2(280)
execution has been completed.
Several cycles may be required before RD2(280) execution is completed. Dur-
ing that time, the execution condition for RD2(28) must remain ON.
RD2(280) carries out data exchange with the Special I/O Unit via the I/O area, so
the time required to complete execution depends on the I/O refresh interval (i.e.,
the cycle time).
Be sure that there is a Special I/O Unit mounted. If no Special I/O Unit is
mounted, RD2(280) execution will continue without stopping.
As of this printing, the RD2(280) can only be used with the C500-CT021 High-
speed Counter Unit is set to four-word operation (normally, when used with SYS-
MAC BUS).
Note Refer to page 101 for general precautions on operand data areas.
ER (A50003):
CY (A50004):
EQ (A50006):
LSB
Number of words to be read (binary 00 to FF)
Beginning address to be read (binary 00 to FF)
Beginning address plus number of words exceeds 100 binary.
Content of *DM word is not BCD when set for BCD.
An error has occurred at the Special I/O Unit.
The read operation has been completed.
Section 5-33
CIO, G, A, T, C, #, DM, DR, IR
CIO
CIO, G, A, T, C, DM
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