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8-3
Section
SRM1(-V2) Cycle Time and I/O Response Time
538
8-3-2 SRM1(-V2) Cycle Time
The processes involved in a single SRM1(-V2) cycle are shown in the following
table, and their respective processing times are explained.
Process
Content
Time requirements
Overseeing
Setting cycle watchdog timer, UM check, etc.
0.18 ms
CompoBus/S end wait
Waiting for CompoBus/S processing to finish
CompoBus/S communications re-
sponse time – Overseeing time –
RS-232C port servicing time – periph-
eral port servicing time
Input refreshing
Input information is read to input bits.
0.02 ms
Program execution
User program is executed.
Refer to
8-3-6 SRM1(-V2) Instruction Execution
Times
.
Total time for executing instructions.
(Varies according to content of user’s
program.)
Cycle time calculation
Standby until set time, when minimum cycle time is
set in DM 6619 of PC Setup.
Calculation of cycle time.
Almost instantaneous, except for
standby processing.
Output refreshing
Output information (results of executing program) is
written to output bits.
CompoBus/S communications are started.
0.05 ms
RS-232C port servicing
Devices connected to RS-232C port serviced.
5% or less of cycle time, but always
between 0.55 and 131 ms
(Set in DM 6616.)
Peripheral port servicing
Devices connected to peripheral port serviced.
5% or less of cycle time, but always
between 0.55 and 131 ms
(Set in DM 6617.)
Minimum Cycle Time
In SRM1(-V2) PCs, CompoBus/S communications are started after the output
refresh is completed. As a result, when the overseeing time plus the RS-232C
port servicing time plus the peripheral port servicing time is shorter than the
CompoBus/S communications response time, processing is placed on stand-by
until CompoBus/S communications are completed.
The minimum cycle time therefore is the the CompoBus/S communications re-
sponse time plus the program execution time plus the input refresh time plus the
output refresh time. The CompoBus/S communications response time depends
on the “maximum number of nodes” and “communications mode” settings, as
follows:
Max. number of nodes Communications mode
CompoBus/S response time
32
High-speed mode
0.8 ms
Long-distance mode
6.0 ms
16
High-speed mode
0.5 ms
Long-distance mode
4.0 ms
Note
The maximum number of nodes and communications mode are set in the PC
Setup (DM 6603).