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Instruction Set and Program Flow Control in HC11 Microcontroller, Slides of Microprocessor and Interfacing

Punjab Engineering CollegeMicroprocessor and Interfacing

An overview of the instruction set and program flow control in the hc11 microcontroller. It covers stack and index register instructions, data manipulation, register interchange instructions, and program flow control instructions such as conditional branches and jumps. The document also includes examples and calculations for using time delays and branches.

Typology: Slides

2012/2013

Uploaded on 05/07/2013

anjushree
anjushree 🇮🇳

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Lecture Overview
–Stack and index register instructions
–The remaining instructions classes are for program
flow control
•Branch Instructions
•Jump Instructions
•Subroutine Calls
•No Operation
•Stop
•REF: Chapter 3 and the appendix that details
the instructions.
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Download Instruction Set and Program Flow Control in HC11 Microcontroller and more Slides Microprocessor and Interfacing in PDF only on Docsity!

Lecture Overview

  • Stack and index register instructions
  • The remaining instructions classes are for program flow control - Branch Instructions - Jump Instructions - Subroutine Calls - No Operation - Stop
  • REF: Chapter 3 and the appendix that details the instructions.

Stack &Index register instructions

  • These instructions allow manipulation of the index registers, X and Y, and exchange with the D accumulator. Additionally, they provide the ability to push and pop X and Y to/from the stack.
  • This class of instructions can be further subdivided into sub-classes of the type of operation.

Data manipulation of contents

  • Add the B accumulator to and index register
    • ABX ABY
    • Does not affect the CC register
  • Data testing of contents of index register
    • CPX CPY
    • There are compares to a 16-bit value in memory

Move the X and Y index registers

  • Push them on the stack – copy the value in the register to the top of the stack. The register stays the same value. These are 2 byte push and pop operations. - PSHX PSHY
  • Pull the top 2 bytes from the stack into X or Y
    • PULX PULY
  • Store the X or Y index register or the SP
    • STX STY STS
  • Load the X or Y index register or the SP
    • LDX LDY LDS

Register interchange instructions

  • Values before execution
    • SP -- $C
    • X -- $000C
  • Execute a TSX instruction
  • Values now
    • SP -- $C
    • X -- $C
  • X is loaded with 1 plus the contents of the stack pointer so that it points to the last value that was stored on the stack.
  • • Ended here on Fri Jan 27,

Conditional Branches

  • These are instructions to the control the flow of execution based on a value in the condition code register.
  • Their general execution is:
    • If the condition tested is false execution continues with the next instruction.
    • If the condition tested is true then execution continues at the relative location indicated in the argument of the instruction.

The effect of a branch

  • A branch controls the flow of execution

Relative addressing mode

  • Relative means the address is related to something.
  • It is related to the current instruction address which is in the program counter (PC). The instruction argument is the offset to be taken if the condition is TRUE.
  • The offset can be positive of negative. It is an 8 bit quantity that is treated as a 2’s complement value and allows offsets of - to +127. Docsity.com

An example

  • This is a timing delay loop
    • DECB takes 1usec
    • BNE takes 1.5 usec
    • LDAB immediate mode takes 1us
  • Coding
  • LDAB #$ count
  • DELAY: DECB
  • BNE DELAY
    • Time delay = 1us+(1us+1.5us)*count

Simple Branches summary

  • Branch on Carry Set of Carry Clear
    • BCS BCC
  • Branch on Zero
    • Equal to zero – BEQ Not Equal to zero – BNE
  • Branch on Minus – BMI
  • Branch on Plus – BPL
  • Branch on Overflow clear or set
    • BVC BVS

Unsigned Binary Branches

  • Branch if higher BHI
    • CMPA $D380 compares A to the contents of $D
    • BHI will branch if A > $D380 i.e. A > M
  • Branch on higher or same BHS
    • BHI is >
    • BHS is a ≥ test
  • Branch if lower BLO <
  • Branch if lower or equal BLS ≤

Jump and Branch always

  • Sometimes called unconditional branches
  • Transfers control to the location specified in the argument of the instruction.
  • Jump, JMP, uses direct, extended, or indexed addressing for the target address
  • Branch always – BRA – us a relative transfer

Subroutines

  • High level languages and good programming practice use subroutines.
  • The 68HC11 has two branches to subroutine
  • and one return from subroutine
  • The BSR is a relative branch to subroutine