Problem 4: Interrupts [25 Points] a) Provide instructions needed to enable inter
ID: 3536268 • Letter: P
Question
Problem 4: Interrupts [25 Points]
a) Provide instructions needed to enable
interrupts, both external and internal
b) Provide instructions you would use to disable interrupts, both
internal and external.
c) For 68HC 11, if interrupts are disabled does it mean that the CPU
will not recognize them at all, or would they be queued as pending interrupts?
d) Does the software interrupt have a mask i.e. does it need to be
disabled and enabled by setting bits of the condition code register
appropriately?
e) LDX #$1000
BSET $39, X $20
Which register
is affected by the BSET instruction?
What bit of this
register is affected and how? i.e. is it made a logic 1 or logic 0?
Explanation / Answer
For the 80x86 256 different interrupts (ranging from 0-255) are available in total. Intel has reserved the first 32 interrupts for exclusive use by the processor but this unfortunately hasn't prevented IBM from placing all hardware interrupts and the interrupts of the PC BIOS in exactly this region which can give rise to some strange situations.
Speaking of hardware interrupts, you can distinguish three types of interrupts:
- Software Interrupts
- Hardware Interrupts
- Exceptions