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

Define target _blank, TARGET = "_blank" "_blank" opens new document in...

TARGET = "_blank" "_blank" opens new document in a new window. Run the code given in Figure and check how it works. This value doesn't require the use of any frames. "_blank"

Illustrate working of rubber dome keyboards, Q. Illustrate working of rubbe...

Q. Illustrate working of rubber dome keyboards? Rubber Dome: In rubber dome keyboards both positioning and contact are controlled by a puckered sheet of elastomer that is a s

What is assembly language, What is assembly language? A complete set of...

What is assembly language? A complete set of symbolic names and rules for the use of machines comprise a programming language, usually referred to as an assembly language.

Search in problem solving - artificial intelligence, Search in Problem Sol...

Search in Problem Solving: If Artificial Intelligence can inform that the other science about anything, it is about problem solving and, in particular, how to research after s

Android mobile application, Students are needed to work in group of 3 and m...

Students are needed to work in group of 3 and make an Android mobile application falling under the following categories: Multimedia o    Eg: Camera app, mp3 player, ga

Difference between write back and write through cache, What is Difference b...

What is Difference between write back and write through cache? A caching method wherein modifications to data into the cache aren't copied to the cache source till absolutely n

Define busy waiting and spinlock, Define busy waiting and spinlock.  Wh...

Define busy waiting and spinlock.  When a process is in its critical section, any other process that tries to enter its critical section must loop continuously in the entry cod

What features are needed to implement top down parsing, The features are ne...

The features are needed to implement top down parsing are? Ans. Source string marker, Prediction making mechanism and also matching and backtracking mechanism features are need

Design principles, The usability and user experience goalsprovidet heintera...

The usability and user experience goalsprovidet heinteraction designer with high-level goals for the interactivep roduct. Thenextissueis how to design a product that satisfies thes

What do you mean by system calls, What do you mean by system calls? Sys...

What do you mean by system calls? System calls give the interface among a process and the operating system. When a system call is executed, it is treated as by the hardware as

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