Rockwell Automation 1747-PT1, D1747NP002 Hand-Held Terminal - Manual (Page 423)

Interrupts – 5/02 Processor Only
Chapter 30
Understanding Selectable Timed
30–3
Interrupt Priorities
Interrupt priorities are as follows:
1. Fault routine
2. STI subroutine
3. I/O interrupt subroutine (ISR)
An executing interrupt can only be interrupted by an interrupt having higher
priority.
Status File Data Saved
Data in the following words is saved on entry to the STI subroutine and
re-written upon exiting the STI subroutine.
•
S:0 Arithmetic flags
•
S:13 and S:14 Math register
•
S:24 Index register