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Scheduled Interrupts
Hardware time clock
Scheduled interrupt
subroutine execution
t3
Scheduled in-
terrupt interval
t3 t3t3
t3 = Software interrupt response time
Total interrupt response time = t3 (software interrupt response time)
The software interrupt response time depends on the interrupt response param-
eter setting in DM 6620 of the PC Setup. If the DM 6620 is set for the C200H-
compatible mode (0000), the software interrupt response time is less than
10 ms. If the DM 6620 is set for the C200HS mode (1xxx), the software interrupt
response time is less than 1 ms. The total interrupt response time is thus as
shown in the following table.
Interrupt response setting Total interrupt response time
C200H-compatible mode Total of following: Special I/O processing time,
Remote I/O processing time, Host Link
servicing time, instruction execution
C200HS mode 1.0 ms or less
Note 1. If there is any instruction in the program that requires longer than 10 ms to
execute when using the C200H-compatible mode, the total interrupt re-
sponse time will be equal to the execution time of the instruction requiring
longer than 10 ms.
2. The above calculations assume that only one interrupt requires executed at
any one time. If multiple interrupts are generated at the same time, execu-
tion of all but the first interrupt will go on standby, increasing the response
times given above.
3. If SYSMAC NET/SYSMAC LINK Units are being serviced when an interrupt
occurs, the interrupt will not be processed until SYSMAC NET/SYSMAC
LINK Unit servicing has been completed. The response times in this case
will be as shown in the following table and will not be affected by the interrupt
response setting.
Interrupt Total interrupt response time
Input interrupt 10.2 ms max.
Scheduled interrupt 10 ms max.
Interrupt Processing Time The processing time from receiving an interrupt input, through program execu-
tion, and until a return is made to the original program location is described next.
The limit of the count frequency resulting from using the scheduled interrupt pe-
riod or input interrupts as the count input is determined by the interrupt proces-
sing time.
Interrupt processing time =
Total interrupt response time + Interrupt program execution time +
Interrupt return time
The interrupt program execution time is determined by the content of the inter-
rupt subroutine. This time is negligible f only SBN(92) and RET(93) are
executed.
The interrupt return time is 0.04 ms.
I/O Response Time Section 6-4