458
SYSMAC BUS/2 I/O refreshing of Units in a SYSMAC BUS/2 System can be disabled by turning
ON the corresponding CPU Bus Service Disable Bits in A015. Bits 00 to 15
correspond to Units #0 to #15, respectively. Turn the bits OFF again to enable
service and resume I/O refreshing.
Asynchronous operation Synchronous operation
I/O refreshing takes place once each
communications cycle.
(Refer to the
SYSMAC BUS/2 Remote
I/O System Manual
for details on the
communications cycle.)
I/O refreshing takes place once each
PC cycle, but I/O points in the SYSMAC
BUS/2 System may not be refreshed
every cycle if the SYSMAC BUS/2
communications cycle is longer than
the PC cycle.
SYSMAC BUS I/O refreshing of Units in a SYSMAC BUS System can be disabled by turning ON
bit A01705 (the I/O Refresh Disable Bit). Turn A01705 OFF again to resume I/O
refreshing.
Asynchronous operation Synchronous operation
I/O refreshing takes place at regular
intervals. The length of the interval
depends on the number of Masters.
Multiply the number of Masters
connected by 5 ms to calculate the
interval.
I/O refreshing takes place once each
PC cycle.
6-1-5 Power OFF Operation
This section details CPU operation when power is turned OFF and ON, and dur-
ing a momentary power interruption.
Power OFF/ON
The following diagram and explanation show the CPU operation when the power
goes off and when power is turned on.
Power supply
Power interruption
signal
Program execution
Momentary Power
Interruption Flag
(A40202)
CPU reset signal
RUN output
85%
Power interruption detection
time: 10 to 25 ms for AC power,
0.3 to 1 ms for DC power
Initialization processing
Normal
Power OFF
interrupt program
Power ON interrupt
program
Shutdown processing
Normal
Stops
Standby
Power interruption
Momentary power interruption
time (default: 0 ms)
Power hold time: 10 ms (fixed)
The following list shows CPU operation when power is interrupted.
1, 2, 3...
1. A power interruption signal is output when the CPU detects a power supply
voltage below 85% of full power. It takes the CPU between 10 ms and 25 ms
to detect the power interruption with an AC power supply and between
0.3 ms and 1 ms to detect the power interruption with a DC power supply.
2. When the power interruption signal is output, program execution is stopped
and the system shutdown procedure (1 ms) takes place. At this point, output
status and timer PV status are maintained.
Power OFF Operation
PC Operation Section 6-1
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