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

Which of the logic gates are known as universal gates, Which of the logic g...

Which of the logic gates are known as universal gates ? Ans. NAND and NOR are termed as universal gates, since any digital circuit can be realized completely by using either of

What are qualified associations, What are qualified associations? A qua...

What are qualified associations? A qualified association is an association in which an attribute known as the qualifier disambiguates the object many associated end.

stores on each line a part number, Make a file "parts_inv.dat" that stores...

Make a file "parts_inv.dat" that stores on each line a part number, cost, and quantity in inventory, e.g.: 123 5.99 52 456 3.97 100 333 2.22 567 Use fscanf to read this infor

Interface constructors, Describe a interface 'Human' with methods as walk' ...

Describe a interface 'Human' with methods as walk' and 'speak'. Describe a class 'User' implementing 'Human'. Describe a work() method in User class.Add a class 'Person' also execu

Subtraction 11011-11001 using 2's complement, Subtraction 11011-11001 using...

Subtraction 11011-11001 using 2's complement. Ans. 11011 - 11001 = A - B 2's complement of B = 00111 1 1 0 1 1 + 0 0 1 1 1 1 0 0 0 1 0 Ignore carry to get answer as 00010 = 2.

Factors of information system which affect the business, Q. Factors of Info...

Q. Factors of Information system which affect the business? There are several factors which affect the business such as - a) Threats of fresh entrants. b) Rivalry surro

What is anonymous file transfer protocol, What is Anonymous File Transfer P...

What is Anonymous File Transfer Protocol? Anonymous FTP: While a FTP client contacts a server, in that case, the daemon will ask for an account number or username and it

Appropriate problems for ann learning, Appropriate Problems for ANN learnin...

Appropriate Problems for ANN learning: Conversely as we did for decision trees there it's important to know where ANNs are the right representation scheme for such job. Howeve

Vector, Explain the characteristics of vector processing

Explain the characteristics of vector processing

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