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 are the limitations of traditional payment instruments, What are the l...

What are the limitations of traditional payment instruments? The limitations of traditional payment system are that they take a lot of time.  These systems needs manual work to

What will exactly the hide statement do, What will exactly the hide stateme...

What will exactly the hide statement do? For displaying the details on secondary lists needs that you have previously stored the contents of the selected line from within the

Explain the various interface circuits, Explain the various interface circu...

Explain the various interface circuits.  An I/O interface having of circuitry required to connect an I/O device to computer bus. One side having of a data path with its associa

Example of perceptrons, Example of perceptrons: Here as an example fun...

Example of perceptrons: Here as an example function in which the AND boolean function outputs a 1 only but if both inputs are 1 and where the OR function only outputs a 1 then

Illustrate associative memory, Q. Illustrate Associative Memory? The ti...

Q. Illustrate Associative Memory? The time required to find an item which is stored in memory can be decreased significantly if stored data can be identified for access by cont

Combinational logic, At a particular moment in time the output of a COMBINA...

At a particular moment in time the output of a COMBINATIONAL logic circuit depends uponthe inputs to the circuit at the same instant.(Unlike sequential logic circuits where the out

Explain about subsystem and object of object oriented, Explain about subsys...

Explain about subsystem and object of object oriented modeling A subsystem is a grouping of elements of that constitutes a specification of behaviour offered by other contained

Explain the trackball and thumbwheel devices, Explain the Trackball and Thu...

Explain the Trackball and Thumbwheel devices  Joysticks A joystick consists of a small, vertical lever (called the stick) mounted on a base that is used to steer the screen

Basic need of search engines, Q. Basic need of Search Engines? Search E...

Q. Basic need of Search Engines? Search Engines are programs which search the web. Web is a big graph with pages being the nodes and hyperlinks being the arcs. Search engines c

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