8-1
Section
CPM1/CPM1A Cycle Time and I/O Response Time
517
8-1-5 Interrupt Processing Time
This section explains the processing times involved from the time an interrupt is
executed until the interrupt processing routine is called, and from the time an in-
terrupt processing routine is completed until returning to the initial location. This
explanation applies to input interrupts, interval timer interrupts, and high-speed
counter interrupts.
1, 2, 3...
1. Source of interrupt
2. Interrupt ON delay
3. Wait for completion of interrupt-mask processing
4. Change to interrupt processing
5. Interrupt routing (CPM1A only)
6. Return to initial location
The table below shows the times involved from the generation of an interrupt sig-
nal until the interrupt processing routine is called, and from when the interrupt
processing routine is completed until returning to the original position.
Item
Contents
Time
Interrupt ON delay
This is the delay time from the time the interrupt input bit turns ON until the
time that the interrupt is executed. This is unrelated to other interrupts.
100
µ
s
Wait for completion of
interrupt-mask processing
This is the time during which interrupts are waiting until processing has
been completed. This situation occurs when a mask processes is
executed. It is explained below in more detail.
See below.
Change to interrupt
processing
This is the time it takes to change processing to an interrupt.
30
µ
s
Return
This is the time it takes, from execution of RET(93), to return to the proces-
sing that was interrupted.
30
µ
s
Mask Processing
Interrupts are masked during processing of the operations described below. Un-
til the processing is completed, any interrupts will remain masked for the indi-
cated times.
Generation and clearing of non-fatal errors:
When a non-fatal error is generated and the error contents are registered at
the CPM1, or when an error is being cleared, interrupts will be masked for a
maximum of 100
µ
s until the processing has been completed.
Online editing:
Interrupts will be masked for a maximum of 600 ms (i.e.: editing DM 6144 to
DM 6655) when online editing is executed during operation. In addition, the
system processing may have to wait for a maximum of 170
µ
s during this
processing.
Example Calculation
This example shows the interrupt response time (i.e., the time from when the
interrupt input turns ON until the start of the interrupt processing routine) when
input interrupts are used under the conditions shown below.
Minimum Response Time
Interrupt ON delay:
100
µ
s
Interrupt mask standby time:
0
µ
s
+
Change-to-interrupt processing:
30
µ
s
Minimum response time:
130
µ
s
Maximum Response Time
(Except for the Online Editing of DM 6144 to DM6655)
Interrupt ON delay:
100
µ
s
Interrupt mask standby time:
170
µ
s
+
Change-to-interrupt processing:
30
µ
s
Maximum response time:
300
µ
s
