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

My project has not working, my project is in .net of lan chatting its have ...

my project is in .net of lan chatting its have tcp\ip connection problem

Explain simple telephone communication system, Explain simple telephone com...

Explain simple telephone communication system with circuit and equation of current flow in microphone? Simple Telephone Communication: In the simplest type of a telephone cir

Microprocessor and interfacing, Write an ALP to count positve and numbers f...

Write an ALP to count positve and numbers from array.

Define bcd, Define BCD. A binary code that distinguishes between 10 ele...

Define BCD. A binary code that distinguishes between 10 elements must contain at least 4 bits, but 6 combinations will remain unassigned. Numerous dissimilar codes can be obtai

Role of internet, Role of Internet, Intranet and extranet in e-business ...

Role of Internet, Intranet and extranet in e-business The following information activities are carried out in many business: 1.  Selling of raw materials 2.  Advertising o

Why digital computers use complemented subtraction method, The chief reason...

The chief reason why digital computers use complemented subtraction is that it ? Ans. By using complemented subtraction method negative numbers can easily be subtracted.

Explain approaches to identify free memory area in a heap, Discuss two main...

Discuss two main approaches to identify free memory area in a heap. Two popular systems to identify free memory areas as a result of allocation and de-allocations in a heap are

Generic techniques developed - artificial intelligence, Generic Techniques ...

Generic Techniques Developed: In the pursuit of solutions to various problems in the above categories, various individual fundamental techniques have sprung up which have been

What are the digital certificates of hardware computations, What are the Di...

What are the Digital certificates of hardware computations Digital certificates are highly dependent on hardware computations, it is essential that mechanisms are evolved to i

Subtract, Write the Add/subtract rule for floating point numbers. Ans:...

Write the Add/subtract rule for floating point numbers. Ans: a. Select the number with the smaller exponent and shift its mantissa right a number of steps equal to the differe

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