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C1000H and C2000H Systems
Transmission Time for
Remote I/O Errors
6-3
C1000H and C2000H Systems
Remote I/O Transmission
Times
Minimum I/O Response
Times
Maximum I/O Response
Times
Example Computations
a Master and four words allocated on the Slave Rack. Because there is only one
Slave, T
and T
are the same.
RM
RT
T
=
1.4 + (0.2 x 4) = 2.2 ms
RT
T
=
2.2 ms
RM
Minimum I/O Response Time
Time = 10 ms + 20 ms + 2.2 ms + 10 ms
= 42.2 ms
Maximum I/O Response Time
Time = 10 ms + (20 ms x 2) + (2.2 ms x 2) + 2.2 ms + 10 ms
= 66.6 ms
The above computations assume that there is no remote I/O error (including
power interruptions). If an error occurs for a Slave, the response time would be
increased by 20 ms for each Slave connected to the same Master as the Slave
where the error occurred. If an error occurs for a Optical I/O Unit, the overall de-
lay time would be increased by 5 ms for each Optical I/O Unit connected to the
same Master as the Optical I/O Unit where the error occurred.
With C1000H and C2000H Remote I/O Systems, both the scan time of the PC
and the transmission time required by the Remote I/O System need to be con-
sidered in computing the I/O response times.
The remote I/O transmission time is computed as follows:
T
= Total Slave transmission time for one Master
RM
ΣT
=
+ T
RT
TT
T
=
Transmission time for each Slave
RT
=
1.4 ms + (0.2 ms x n)
Where n = number of I/O words on the Slave Rack
T
=
Optical I/O Unit transmission time
TT
=
0.2 ms x m
Where m = number of Optical I/O Units
The minimum response time occurs when all signals are processed as soon as
they are received. Because remote I/O processing is handled in parallel with
program execution, two scans are required so that the program is executed.
Time = Input ON delay + scan time x 2 + T
The maximum response time occurs when the input just misses both the first
remote I/O transmission and the program execution portion of the scan, mean-
ing that processing must wait for the next transmission and then the next (i.e.,
the third) scan.
Time = Input ON delay + scan time x 3 + T
Calculations would be as shown below for input and output ON delays of 10 ms
and a scan time of 20 ms. This example uses a C1000H system with only one
Slave Rack connected to a Master and four words allocated on the Slave Rack.
Because there is only one Slave, T
T
=
1.4 + (0.2 x 4) = 2.2 ms
RT
T
=
2.2 ms
RM
Minimum I/O Response Time
Time = 10 ms + 20 ms x 2 + 2.2 ms + 10 ms
= 62.2 ms
+ output ON delay
RM
x 2 + T
+ output ON delay
RM
RT
and T
are the same.
RM
RT
Section
6-3
73
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