Introduction; C500 Systems - Omron C120 System Manual

C500 Systems

6-1

Introduction

Caution
!
6-2 C500 Systems
Remote I/O Transmission
Times
Minimum I/O Response
Times
Maximum I/O Response
Times
Example Computations
72
The time required to produce a programmed output to an input within a Remote
I/O System varies with the scan time of the PC, the transmission time of the Re-
mote 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 subsection.
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 in which processing occurs during the PC scan, particular that inputs will
not produce programmed actions until the program has been executed.
Input on
Slave Rack
When calculating the response times involving inputs and outputs from another
CPU connected by an I/O Link Unit, the scan time of the controlling CPU and the
scan time of the PC to which the I/O Link Unit is mounted must both be consid-
ered.
Noise may increase I/O delays.
With C500 Remote I/O Systems, both the scan time of the PC and the transmis-
sion time required by the Remote I/O System need to be considered in comput-
ing 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, meaning only one scan is required to execute the program
before the output is made.
Time = Input ON delay + scan time + 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 scan.
Time = Input ON delay + scan time x 2 + 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 only one Slave Rack connected to
Section
Output on
Slave Rack
X
+ output ON delay
RM
x 2 + T + output ON delay
RM RT
6-2