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

Differentiate b/w pre-emptive and non-pre-emptive scheduling, Differentiate...

Differentiate between pre-emptive and non-pre-emptive scheduling. Pre-emptive scheduling : in its approach, center processing unit can be taken away from a process if there is a

NETWORK ADMIN, Ask qDiscuss the risks of having a single root user and how ...

Ask qDiscuss the risks of having a single root user and how more limited management abilities can be given to others users on Linux/UNIX systems.uestion #Minimum 100 words accepted

Define access time for magnetic disk, Define access time for magnetic disk....

Define access time for magnetic disk. The sum of seek time and rotational delay is known as access time for disks. Normal 0 false false false EN-IN

Explain function of dual slope analogue to digital converter, Draw and expl...

Draw and explain the function of dual slope analogue to digital converter. Derive the equations used. Ans.               Dual slope A/D converter : This has 4 main blocks.

Executing a parallel algorithm, Q. Executing a parallel algorithm? Mult...

Q. Executing a parallel algorithm? Multiple processors need synchronization with one another when executing a parallel algorithm. So task which is running on processor X may ha

C, "Super ASCII", if it contains the character frequency equal to their asc...

"Super ASCII", if it contains the character frequency equal to their ascii values. String will contain only lower case alphabets (''a''-''z'') and the ascii values will starts from

Forward chaining, Forward Chaining: Now we have suppose we have a set ...

Forward Chaining: Now we have suppose we have a set of axioms that we know are true statements about the world. Whether we set these to each be an initial state of the segoal

Compare putchar function with the getchar function, Normal 0 fa...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

What happens if acknowledge() is called within a transaction, As per the JM...

As per the JMS specification, when you are in a transaction, the acknowledge Mode is ignored. If acknowledge() is known as within a transaction, it is ignored.

Explain redundant array of independent disks levels, Q. Explain Redundant A...

Q. Explain Redundant Array of Independent Disks levels? One such industrial standard that exists for multiple-disk database schemes is called as RAID which implies Redundant Ar

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