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

Name the appliances which are controlled by micro-processor, Name the appli...

Name the appliances which are controlled by micro-processor Many household appliances which are microprocessor-controlled do not have operating systems (for example microwave o

Define terms setup time and hold time violation, Define setup time and hold...

Define setup time and hold time, what will occur when there is setup time and hold tine violation, how to overcome it? For Synchronous flip-flops, we have particular requiremen

Functions for message passing, Functions for Message Passing: MPI proc...

Functions for Message Passing: MPI processes don't share memory space and one process can't directly access other process's variables. Therefore they need some form of communi

What is external procedures, Q. What is External Procedures? These proc...

Q. What is External Procedures? These procedures are written as well as assembled in separate assembly modules and afterwards linked together with the main program to form a bi

Explain optimizing transformations, Explain optimizing transformations? ...

Explain optimizing transformations? Optimizing transformations: It is a rule for rewriting a segment of a program to enhance its execution efficiency without influencing i

State a simple pull transaction, a. Explain the future of mobile commerce i...

a. Explain the future of mobile commerce in world? b. 'Push and Pull' are two ways of transferring information to and from a phone, through WAP. Now, with the help of diagram, s

Define static memories, Define static memories? Memories that consists ...

Define static memories? Memories that consists of circuits capable of retaining their state as long as power is applied is known as static memories

Explain the term electronic data interchange (edi), Explain the term Electr...

Explain the term Electronic Data Interchange (EDI). Electronic Data Interchange (EDI) may be generally easy to understand as the replacement of paper-based purchase orders alon

Control signals from control bus, Control Signals from Control Bus: A numb...

Control Signals from Control Bus: A number of the control signals are provided to control unit by the control bus. These signals are issued from outside the CPU.  Some of these si

What is an operating system, What is an operating system?  An operating...

What is an operating system?  An operating system is a program that handles the computer hardware. It acts as an intermediate among users of a computer and the computer hardwar

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