I/O Refreshing - Omron SYSMAC CV Series Operation Manual

PC Operation
AC power supply
Zero-cross signal
PC operation
Caution
!
IORF(184) Refreshing
Immediate Refreshing
SYSMAC BUS/2 and SYSMAC BUS Systems
As shown in the following diagram, output points are refreshed (A) when the zero
voltage signal is received, the program is executed (B), input points are re-
freshed (C), and the CPU waits for the next zero voltage signal (D). If I/O refresh-
ing and program execution exceed one half the AC cycle (B'), the next output
refreshing will occur when the next zero voltage signal is received.
A B C D A B C
Do not use zero-cross refreshing with the CV2000 or CVM1-CPU21-EV2 if the
number of points output from the PC is greater than 1,024 (64 words). If zero-
cross refreshing is used with more than 1,024 output points, zero-cross effec-
tiveness will be lost for all outputs past the first 1,024 in memory.
IORF(184) requires two operands, St and E, which define the first and last word
in a group of I/O words. When IORF(184) is executed, all words between St and
E are refreshed. This is in addition to the I/O refreshing performed by the I/O re-
freshing method selected in the PC Setup. Refer to 5-27-4 I/O REFRESH –
IORF(184) for details.
Immediate refreshing refreshes the input/output points affected by an instruc-
tion immediately before/after the instruction is executed; this is in addition to the
I/O refreshing performed by the I/O refreshing method selected in the PC Setup.
Immediate refreshing is available for many instructions and is selected by enter-
ing a "!" prefix before the instruction when writing the program. Only I/O points
allocated to I/O Units (except High-density I/O Units using dynamic I/O)
mounted on a CPU Rack, Expansion CPU Rack, or Expansion I/O Rack can be
refreshed with immediate refreshing.
The five methods for refreshing I/O described above cannot be used for I/O
points allocated in SYSMAC BUS/2 and SYSMAC BUS Systems. Refreshing of
I/O points in SYSMAC BUS/2 and SYSMAC BUS Systems differs for synchro-
nous and asynchronous operation, as shown in the following tables.
D A B' C
A: Output points are refreshed
B: Program is executed
B': I/O refreshing and program execution
exceed one half the AC cycle
C: Input points are refreshed
D: CPU waits for the next zero voltage signal
Section 6-1
D A
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