146
The PC takes longest to respond when it receives the input signal just after
the input refresh phase of the cycle. In this case the CPU does not recognize
the input signal until the end of the next cycle. The maximum response time
is thus one cycle longer than the minimum I/O response time, except that the
input refresh time would not need to be added in because the input comes
just after it rather than before it.
Input
signal
Output
signal
Cycle
Cycle time
I/O refresh
I/O response time
CPU reads
input signal
CPU writes
output signal
Output ON delay
Input ON delay
Overseeing
Cycle time
Maximum I/O response time = input ON delay + (cycle time x 2) + overseeing
time + output ON delay
The data in the following table would produce the minimum and maximum
cycle times shown calculated below.
Input ON-delay
1.5 ms
Cycle time
20 ms
Input refresh time
0.23 ms
Overseeing time
3.0 ms
Output ON-delay
15 ms
Minimum I/O response time = 1.5 + 20 + 0.23 + 3.0 +15 = 39.73 ms
Maximum I/O response time = 1.5 + (20 x 2) + 3.0 +15 = 59.5 ms
Maximum I/O Response
Time
Calculation Example
I/O Response Time
Section 6-5
Summary of Contents for SYSMAC C20K
Page 1: ...Cat No W146 E1 5 Programmable Controllers SYSMAC C20K C28K C40K C60K ...
Page 2: ...K type Programmable Controllers OPERATION MANUAL Revised July 1999 ...
Page 3: ...iv ...
Page 5: ...vi ...
Page 19: ...7 SECTION 2 Hardware Considerations 2 1 Introduction 2 2 Indicators 2 3 PC Configuration ...