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6-1-3 Synchronous Operation
PC operation can be set to synchronous operation in the PC Setup to syn-
chronize instruction execution and peripheral servicing. The following dia-
gram shows CPU operation during synchronous operation.
Basic processes
Cycle time and
Write I/O memory
Write program
Read program
Monitoring
Forced Set/Reset
processing
Execute program
Refresh timers
Basic processes
Synchronizing
Peripheral device servicing
Host Link servicing
CPU bus check
Memory check
Battery check
Clock update
Start input check
Unit #0 refreshing
Unit #0 event processing
Interrupt processing:
SYSMAC NET Link refreshing
SYSMAC LINK refreshing
SYSMAC BUS/2 refreshing
CPU Bus Link refreshing (*3)
Interrupt processing (*4):
I/O Interrupt program
Scheduled interrupt program
SYSMAC BUS refreshing
TIMH(015) refreshing (every 10 ms)
Scheduled refreshing
Timer refreshing (every 80 ms)
I/O bus check
Event processing
Input, output, and
SYSMAC BUS refreshing
Synchronizing
CPU Bus Unit servicing (*1)
Waiting
Waiting
Synchronizing
(*2)
Unit #15 refreshing (*2)
Unit #15 event processing
(*3)
(*2)
memory check
Note 1. Only BASIC Units and Personal Computer Units are refreshed in CPU Bus
Unit servicing. Other CPU Bus Units are refreshed in interrupt processing.
2. Interrupts (for SYSMAC NET Link, SYSMAC LINK, and SYSMAC BUS/2 re-
freshing) are processed once each cycle, but if the cycle time is less than the
communications cycle time, these Units might not be serviced every cycle.
3. The CPU Bus Link Area data may not be synchronized even with synchro-
nous operation.
4. I/O interrupts, scheduled interrupts, and scheduled refreshing will be per-
formed even during peripheral servicing.
PC Operation Section 6-1
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