One-Time Counting With Software Start (Ocss) - Siemens SIMATIC S5 IP 281 Equipment Manual

R 11/92

One-Time Counting with Software Start (OCSS)

6.3.3
When the software gate opens, the counter is loaded with the value
Method of
stored in the load register, and begins to count starting with this value.
operation
It is stopped by the following.
– Overflow of the counter
– Underflow of the counter
– The software gate closes.
The counter remains in stop status until the software gate is opened again.
Gate control Software gate control with
Start:
stop:
Evaluation of bit 6 (overflow) and bit 7 (underflow) in status register 1/2 is
Notes
used to determine whether the counter has exceeded a range limit.
This operating mode cannot be set unless the gate function has been en-
abled by the GEN bit (bit 1 in control register 1/2). Otherwise the message
"illegal operating mode" is output (IOM in status register 3) and the ERROR
LED goes on,
The settings must be performed in the sequence listed below.
1. Enable gate function (GEN in control register 1/2)
2. Set operating mode (parameter register 1/2)
AG
1992, Order No: 6ES5 888-0KP21
Underflow
Example:
Counting mode 1
When a range limit is exceeded, the counter stops at this limit
(e.g., in counting mode 1, the counter stops at OOOOH when an un-
derflow occurs and at FFFFH when an overflow occurs).
Operating Modes and Functions
1
FFFF
Load value
Overflow
6 – 9