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145
Function
code
ConditionsExecution
time(
µs)
Instruction
84 SFTR 136 to 668 When resetting 1 to 64 DM words
44 NOP
42 IL
91 SBS 75 Always
92 SBN 26 Always
93 RET 49 Always
97 IORF 108 When refreshing 1 word
6-5 I/O Response Time
The I/O response time is the time it takes for the PC to output a control signal
after it has received an input signal. How long it takes to respond depends on
the cycle time and when the CPU receives the input signal relative to the in-
put refresh period. The I/O response times for a PC not in a Link System are
discussed below. For response times for PCs with Link Systems, refer to the
relevant
System Manual
.
The minimum and maximum I/O response time calculations described below
are for the following, where 0000 is the input bit that receives the signal and
0200 is the output bit corresponding to the desired output point.
0000
0200
The PC responds most quickly when it receives an input signal just prior to
the input refresh period in the cycle. Once the input bit corresponding to the
signal has been turned ON, the program will have to be executed once to
turn ON the output bit for the desired output signal and then the input refresh
and overseeing operations would have to be repeated before the output from
the output bit was refreshed. The I/O response time in this case is thus found
by adding the input ON-delay time, the cycle time, the I/O refresh time, the
overseeing time, and the output ON-delay time. This situation is illustrated
below.
Cycle time
Input
signal
Output
signal
Cycle
Cycle time
I/O refresh
Overseeing
I/O response time
CPU reads
input signal
CPU writes
output signal
Output ON delay
Input ON delay
Minimum I/O response time = Input ON delay + Cycle time + I/O refresh time
+ Overseeing time + Output ON delay
Minimum I/O Response
Time
I/O Response Time Section 6-5