Omron SYSMAC CV Series - IO Response Time; Asynchronous Operation with a SYSMAC BUS System

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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.
Cycle time
Input
signal
Output
signal
Cycle
Cycle time
I/O refresh
Overseeing
I/O response time
CPU reads
input signal
Output ON delay
Input ON delay
CPU writes
output signal
Program execution Program execution
Maximum I/O response time =
input ON delay + (cycle time x 2) + output ON delay
Maximum I/O response time = 1.5 + (20 x 2) +15 = 56.5 ms
6-5-2 Asynchronous Operation with a SYSMAC BUS System
Here, we’ll compute the minimum and maximum I/O response times for a
CV1000 that is set for asynchronous operation and controls a SYSMAC BUS
System with a single Master. Both the input and output are on I/O Units con-
nected to Slave Racks. In asynchronous operation, SYSMAC BUS refreshing
occurs every 5×n ms, where n is the number of Masters mounted, and can occur
at any point of the instruction execution cycle. In this case only one Master is
involved, so refreshing occurs every 5 ms.
The transmission time for a Master is the sum total of the transmission times for
all Slaves connected to it. The transmission time for Slave Racks is 1.4 + (0.2× a )
ms, where a is the number of I/O words on the Slave. The transmission time for
I/O Terminals is 2×b ms, where b is the number of I/O words on the I/O Terminals.
The data in the following table is used to produce the minimum and maximum
cycle times shown calculated below.
Input ON delay 1.5 ms
Cycle time 20 ms
Output ON delay 15 ms
Slave Rack transmission time
1.4 + (0.2×4) = 2.2 ms
I/O Terminal transmission time
2×3 = 6 ms
Master transmission time (T
RM
) 2.2 ms + 6 ms = 8.2 ms
Maximum I/O Response
Time
I/O Response Time Section 6-5