Access To I/Os During Time-Controlled Program Execution; (For S5-95U Only); Access To I/Os During Time-Controlled Program Execution (For S5-95U Only) - Siemens SIMATIC S5-90U System Manual

S5-90U/S5-95U
6.3.2

Access to I/Os During Time-Controlled Program Execution

(for S5-95U only)

The S5-95U enables time-controlled program execution with the OB 13 (see Section 9.1.3).
There are two possibilities for accessing the I/Os during time-controlled program execution:
• Direct I/O access (analogous to cyclic program execution, see Section 6.3.1)
• Indirect I/O access via the interrupt process image.
Indirect I/O Access via the Interrupt Process Image
Information can be exchanged with the external I/Os only via the so-called interrupt process images.
The interrupt process images are used exclusively for time-controlled program execution and are
identical to the "normal" process images.
Procedure for indirect I/O access via the interrupt process image (see Figure 6-12):
1. At the beginning of time-controlled program processing, data is read from the inputs of the
external I/Os into the interrupt PII. They are exclusively available to the time-controlled program.
2. The values in the interrupt PII are processed via the STEP 5 operations of the time-controlled
program.
3. The values in the time-controlled program are written both into the "normal" PIQ and into the
interrupt PIQ using STEP 5 operations.
4. The values in the interrupt PIQ are transferred to the outputs, i.e. all outputs signal states are
updated.
STEP 5 operations suitable for indirect I/O access:
Table 6-6. Indirect I/O Access During Time-Controlled Program Execution -
STEP 5 Operations
Onboard I/Os
Read inputs
Not possible
Not possible
x stands for any permissible address
Note
For time-controlled program execution, the L PY x, L PW x, T PY x and T PW x
operations can be used for
• Direct access to the onboard I/Os
• Indirect access to the external I/Os via the interrupt process image
depending on the address x.
EWA 4NEB 812 6115-02b
Write outputs
Not possible
Not possible
Addressing and Access to I/Os
External I/Os
Read inputs Write outputs
L PY x T PY x
L PW x T PW x
6-13