256
The
PC Setup for the C200HS contains
settings in DM 6620 that disable refresh
-
ing
in the normal cycle for specific Special I/O Units. This settings are as shown
below.
Interrupt mode
(1 = high-speed)
Bit 15
00
1 00**********
Unit #0
Unit #1
.
.
.
Unit #9
DM6620
12
Note Disabling
special I/O refreshing in the normal cycle to refresh special I/O in an
interrupt
subroutine is necessary
only in the high-speed mode. Disabling normal
cycle
refreshing of special I/O during normal interrupt mode will be ignored and
the
special I/O will be refreshed both in the normal cycle
and in the interrupt sub
-
routine.
The execution time of interrupt subroutines must be kept to less than10 ms if the
high-speed interrupt
mode
is used and Special I/O Units, Host Link Units, or Re
-
mote I/O Units are programmed. An interrupt programming error (system FAL
error 8B) will occur if the execution time is 10 ms or greater.
The
execution time of interrupt subroutine with the longest execution time is out
-
put
to SR 262 and the
number of the subroutine with the longest execution time
is output to SR 263.
SR
262
SR 263
0123
80* *
Maximum interrupt subroutine execution time (in 0.1 ms)
No. of interrupt subroutine with maximum execution time
Example: 12.3 ms for subroutine #80
Note The
above 10-ms limit
does not apply when the normal interrupt mode is used or
when the above Units are not mounted.
Data Concurrence Although
data concurrence is not a problem for execution of normal arithmetic
instructions or comparison instructions, it can be a problem when executing
longer instructions that handle multiple words, such as block transfer instruc-
tions,
when the high-speed interrupt mode is used and
the same data is handled
both in the main program and in an interrupt subroutine.
Data
may not be concurrent in two dif
ferent situations: 1) if a data write operation
in
the main program is interrupted and the same data is read in an interrupt sub
-
routine
and 2) if a data read operation in the main program is interrupted and the
same data is written in an interrupt subroutine.
Subroutines and Interrupt Control Section 5-23
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