!
457
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.
AC power supply
Zero-cross signal
PC operation
A DC AB ADC AB DCB’
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
Caution 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) Refreshing 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 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.
SYSMAC BUS/2 and SYSMAC BUS Systems
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.
PC Operation Section 6-1
To Next Page
Loading...
