339
Induction sequence processing: 15 ms x (8 PCs – 8 PCs) = 0 ms
I/O refresh bits for Unit 0 256
I/O refresh bits for Unit 7 256
Reducing Response Time IORF(97)
can be used in programming to shorten the I/O response time
greater
than
is possible by setting a high number of refresh
bits. (Remember
, increasing
the
number of refresh bits set
on the back-panel LED shortens response time,
but increases the cycle time of the PC.)
The following calculations for the maximum cycle time use the same example
System
configuration as that used in 5–2 Response T
imes. In programming the
PCs
for PC Link Units #0 and
#7, IORF(97) is executed during every PC scan for
the
PC Link Units. The basic equation for the maximum I/O response time is as
follows:
Response
time = Input ON delay + [Cycle time of PC
of Unit 0 x (Number of LR
transfer
bits
÷
Number of I/O refresh bits
÷
2)] +
α
+ PC Link
polling time + Induction sequence processing time + {Cycle
time
of PC of Unit 7 x [(Number of LR transfer bits
÷
Number of
I/O refresh bits ÷ 2) x 2 + 1]} + β + Output ON delay
If
cycle time of
PC of Unit 0 > PC Link polling time,
α
= cycle time of PC of Unit 0. If
cycle time of PC of Unit 0 < PC Link polling time, α = PC Link polling time.
If
cycle time of PC of Unit 7 > PC Link polling time,
β
= cycle time of PC of Unit 7. If
cycle time of PC of Unit 7 < PC Link polling time, β = PC Link polling time.
The required data from the example System configuration is as follows:
Input ON delay 1.5 ms
Output ON delay 15 ms
Cycle time of PC of Unit 0 20 ms + 5.7 ms = 25.7
(5.7 ms required for IORF execution)
Cycle time of PC of Unit 7 50 ms + 5.7 ms = 55.7
(5.7 ms required for IORF execution)
Number of PC Link Units 8
Number of LR bits 1,024
Number of refresh bits for Unit 0 256
Number of refresh bits for Unit 7 256
PC Link polling time 2.8 ms x 8 PCs + 10 ms = 32.4 ms
Induction sequence processing time 15 ms x (8 PCs – 8 PCs) = 0 ms
Placing
these values into the equation produces a maximum I/O response time
of 466.9 ms, approximately 200 ms shorter than when IORF is not used.
6-4-5 One-to-one Link I/O Response Time
When
two C200HSs are linked one-to-one, the I/O response time is the time re
-
quired for an input executed at one of the C200HSs to be output to the other
C200HS by means of one-to-one link communications.
One-to-one
link communications
are carried out reciprocally between the mas
-
ter and the slave. The respective transmission times are as shown below, de-
pending on the number of LR words used.
Number of words used Transmission time
64 words (LR 00 to LR 63) 39 ms
32 words (LR 00 to LR 31) 20 ms
16 words (LR 00 to LR 15) 10 ms
I/O Response Time Section 6-4
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