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C500 Systems Section 6-2
6-1 Introduction
The time required to produce a programmed output to an input within a Re-
mote I/O System varies with the scan time of the PC, the transmission time of
the Remote I/O System, and the timing of the input.
The processing that determines and the methods for calculating maximum
and minimum response times from input to output are provided in this sub-
section. Calculations assume that both the input and the output are located
on Slave Racks in a Remote I/O System.
Although more precise equations are possible if required, equations used for
the following calculations do not consider fractions of a scan.
In looking at the following timing charts, it is important to remember the se-
quence processing occurs during the PC scan, particular that inputs will not
produce programmed-actions until the program has been execution.
Input Output
Caution Noise may increase I/O delays.
6-2 C500 Systems
With C500 Remote I/O Systems, both the scan time of the PC and the trans-
mission time required by the Remote I/O System need to be considered in
computing the I/O response times.
The remote I/O transmission time is computed as follows:
TRM = Total Slave transmission time for one Master
= ΣTRT + TTT
TRT = Transmission time for each Slave
= 1.4 ms + (0.2 ms x n)
Where n = number of I/O words on the Slave Rack
T
TT = Remote Terminal transmission time
= 0.2 ms x m
Where m = number of Remote Terminals
The minimum response time occurs when all signals are processed as soon
as they are received, meaning only one scan is required to execute the pro-
gram before the output is made.
Time = Input ON delay + scan time + (T
RT
or TTT) + output ON delay
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,
meaning that processing must wait for the next transmission and then the
next scan.
Time = Input ON delay + (scan time x 2) + (T
RM x 2) + (TRT
or TTT) + output
ON delay
Remote I/O Transmission
Times
Minimum I/O Response
Times
Maximum I/O Response
Times
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