Siemens SIMATIC S5-115U User Manual page 419

S5-115U Manual Integral Blocks
11.2.4 OB254 Read In Digital Input Modules (CPU 944 only)
OB254 (which can be invoked with JU OB254 or JC OB254) transfers the digital inputs to the
process input image (PII). In contrast to cyclic updating of the PII, OB254 does not take bit 1 into
account in system data word RS 120, i.e. the Enable bit for cyclic updating of the PII.
11.2.5 OB255 Transfer the Process Output Image (PIQ) to the Output Modules
(CPU 944 only)
OB255 (which can be invoked with JU OB255 or JC OB255) forwards the process output image to
the digital output modules without regard to bit 2 in system data word RS 120, i.e. the Enable bit
for cyclic output of the PIQ to the digital output modules.
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EWA 4NEB 811 6130-02b