Technical data

Disabling/enabling

process interrupts

Function

Disable external process interrupt servicing

Enable external process interrupt servicing

You can use operations "disable/enable process interrupts", for example

to suppress external process interrupts when you are using time-driven

processing. External process interrupt-driven processing is then no longer

possible in the program section between the IA and RA operations.

See also the special function OB 120 "disable interrupts", Section 6.5.

3.5.5

Semaphore Operations

If two or more CPUs in one programmable controller (see Chapter 10)

require access to the same global memory area (peripherals, CPs, IPs),

there is a danger that one CPU will overwrite the data of another CPU

or that one CPU could read invalid intermediate data statuses of

another CPU and misinterpret them. You must therefore coordinate

CPU accesses to the common memory areas.

You can coordinate the individual CPUs using the SED and SEE

operations.

You can, for example, program the following coordination between two

CPUs: a CPU involved in multiprocessing can only access the common

memory area after it has successfully set a declared semaphore (SES). A

semaphore xx can only be set by a single CPU. If a CPU fails to set (i.e.

disable) the semaphore, it cannot access the memory area. In the same

way, a CPU can no longer access the memory once it has released the

semaphore again (SEE).

Table 3-24 Disabling/enabling process interrupts

Semaphore Operations

CPU 928B Programming Guide

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