Stack operation and interrupts in microprocessor, Computer Engineering

Assignment Help:

Let us review the operation of the stack within the 68HC11, the stack is a defined area of RAM which is last in first out register (LIFO) . Access to the stack is made via a stack pointer (SP). In the 68HC11 there is only one stack pointer and it is initialised by the LDS command. To transfer data onto the stack we can use the command PSHA or PSHB i.e. push register A or B onto the stack. To remove data simply pull it i.e PULA or PULB, likewise the index registers may be stacked  etc.

      PSHA Push A onto Stack
      PSHB  Push B onto Stack
      PSHX  Push X onto Stack
      PSHY  Push Y onto Stack
      PULA Pull A onto Stack
      PULB  Pull B onto Stack
      PULX  Pull X onto Stack
      PULY  Pull Y onto Stack

Every time data is 'Pushed' onto the stack the Stack pointer is decrements accordingly. The stack is used often by the micro controller for temporary holding data, if a subroutine occurs, the processor stacks the return address and upon the receipt of the RTS command, it pulls the return address automatically. During an interrupt the processor stacks the full details of itself i.e.

  SP    Condition code  
  SP-1    Accumulator A
  SP-2    Accumulator B
  SP-3    Index register X high
  SP-4    Index register X low
  SP-5    Index register Y high
  SP-6    Index register Y low
  SP-7    return address High
  SP-8    Return address Low 
  SP-9    Stack pointer after interrupt

Therefore great care should be taken when using the stack as during an interrupt or subroutine if you place data on the stack you must remove the data before you return from it.


Related Discussions:- Stack operation and interrupts in microprocessor

What is the main problem with segmentation, What is the main problem with s...

What is the main problem with segmentation? Problem with segmentation (i) Is with paging, such mapping needs two memory references per logical address that slows down the

What do you mean by segment numbers, Q. What do you mean by Segment numbers...

Q. What do you mean by Segment numbers? There is a good reason for not leaving determination of segment numbers up to assembler. It permits programs written in 8086 assembly

Describe the concepts of information systems delivery cycle, Write a 2-3 pa...

Write a 2-3 page paper (excluding title, abstract, introduction, and references) describing the concepts of the Information Systems Delivery Cycle (SDLC) and how the Project Manage

Explain the process of inter-register signalling, Explain the process of in...

Explain the process of inter-register signalling. Registers are utilized in common control exchanges to store and analyze routing data. They are given on a common basis is a

What is demand paging, What is major difference between the Historic Unix a...

What is major difference between the Historic Unix and the new BSD release of Unix System V in terms of Memory Management? Historic Unix uses Swapping - Whole process is tran

The average height or weight, A script kept information on potential subjec...

A script kept information on potential subjects for an experiment in a vector of structures known as "subjects".  The following show an example of what the contents may be: >> subj

Explain the state space of search problem, Question: (a) Assume you are...

Question: (a) Assume you are a taxi driver. Your taxi can hold four passengers. Passengers pay a flat fee for a ride to the airport, so your goal is to pick up four passengers

Operations from events, Operations from events During analysis, events...

Operations from events During analysis, events which are sent to target objects. An operation on these object are presented as labels on transitions and should not be explicit

Answer, Write a program to find the area under the curve y = f(x) between x...

Write a program to find the area under the curve y = f(x) between x = a and x = b, integrate y = f(x) between the limits of a and b. The area under a curve between two points can b

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd