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Publication 1747-RM001G-EN-P - November 2008

B-36 SLC Status File

S:11

and

S:12

Dynamic Config I/O Slot Enables

These two words are bit mapped to represent the 30

possible I/O slots in an SLC 500 system. S:11/0 represents

I/O slot 0 for fixed I/O systems. (Slot 0 is used for the CPU in

modular systems.) S:11/1 through S:12/14 represent I/O

slots 1-30. S:12/15 is unused.

When a bit is set (default condition), it allows the I/O

module contained in the reference slot to be updated in the

I/O scan of the processor operating cycle.

When you clear a bit, it causes the I/O module in the

referenced slot to be ignored. That is, an I/O slot enable

value of 0 causes the input image data of an input module to

freeze at its last value. Also, the outputs of an output

module will freeze at their last values, regardless of values

contained in the output image. Outputs remain frozen until:

• either power is removed,

• the REM Run mode is exited, or

• a major fault occurs.

At that time the outputs are zeroed, until the slot is again

enabled (set).

Disabled slots do not have to match the user program

configuration.

•••••

ATTENTION

Make certain that you have thoroughly examined the effects

of disabling (clearing) a slot enable bit before doing so in

your application.

TIP

The SLC 5/02 and higher processors inform each specialty

I/O module that has been disabled/enabled. Some I/O

modules may perform other actions when disabled or

re-enabled. Refer to the user information supplied with the

specialty I/O module for possible differences from the above

descriptions.

••••

ATTENTION

The DII instruction ignores the slot enable/disable status.

Do not run the DII on a faulted slot. If you apply the DII on a

disabled slot, the interrupt will occur. However, the input

image will not reflect the present state of the card.

This bit is applied upon detection of a DII Reconfigure bit,

each DII ISR exit, and at each end of scan (END, TND, or

REF).

•••

Table B.4 Status File Functions (Continued)

Address Classification Description Fixed

5/01

5/02 5/03 5/04 5/05