ece 265 – lecture 7 the m68hc11 basic instruction set logical, shift and rotate, data testing...
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ECE 265 – LECTURE 7
The M68HC11 Basic Instruction Set
Logical, Shift and Rotate, Data Testing
04/21/23
1ECE265
Joanne E. DeGroat, OSU
Lecture Overview
The M68HC11 Basic Instruction Set The Logical instructions to perform Boolean
operations The Data Testing The Shift and Rotate instructions
REF: Chapter 3 and the appendix that details the instructions.
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The Logical Instructions
Instructions to perform Boolean operations on data Instructions for AND NOT and OR operation
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AND operation
Description: AND the A (or B) accumulator with the operand of the instruction
CC effects: N Z set per result Forms: ANDA (opr) ANDB(opr)
And can be immediate mode or a memory location ANDA #$FF What does this do? ANDB #$00 What does this do?
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AND operation and masking
Masking is keeping only those bits you are interested in. The reaming bits are “masked” out.
Example ANDA #$0F Keep the lower 4 bits of accum A
If the A accumulator contains a value of $34 Then this operation is A 0011 0100 AND-ed with 0000 1111 giving 0000 0100
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OR operation
Description: OR the A (or B) accumulator with the operand of the instruction
CC effects: N Z set per result Forms: ORA (opr) ORB(opr)
And can be immediate mode or a memory location ORAA #$FF What does this do? ORAB #$00 What does this do?
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Exclusive OR operation
Description: Exclusive OR the A (or B) accumulator with the operand of the instruction
CC effects: N Z set per result Forms: EORA (opr) EORB(opr)
And can be immediate mode or a memory location EORA #$FF What does this do? EORB #$00 What does this do?
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Joanne E. DeGroat, OSU
The NOT or invert operation
Description: Can complement a complete byte in an accumulator or memory. This is a bitwise complement.
CC effect: N V set per data, V cleared, C set Forms: COMA COMB COM (opr)
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Examples
Example instructions Accum A has
val $1C
Memory $D330
val $2F (a) ANDA $D330 (b) EORA $D330 (c) ORAA $D330
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Data Testing Instructions
Will cover the Bit Test and Setting and Clearing of bits.
The branch will be covered with branches.
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Bit test
Description: Compare the operand with the accumulator contents and set the CC bits. Performs a bitwise logical AND.
CC effects: N Z eval V cleared Forms: BITA (opr) BITB (opr) If operand is equal to accumulator Z is set See Appendix A of text for a complete description
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Joanne E. DeGroat, OSU
Clear and set bits in memory
Description: Set or Clear bits in memory according to a mask given in the instruciton.
CC effects: N Z V cleared Forms: BSET (opr) (mask) BCLR (opr) (mask)
Example BSET $0035 $09 Performs a logical OR of the contents of location $35 With $09 and puts the result back in the location. This example will set bits 0 and 3 of the data byte.
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Shift and Rotate Instructions
The instructions perform arithmetic and logical shifts and also rotate the data.
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The effect of shift and rotates
What do the instructions do?
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What is the real effect of
Arithmetic shifts? Do arithmetic shifts have the effect of multiplicaiton?
Unique aspects of logical shifts
Can also do double shifts
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The instructions
Arithmetic Shifts ASL (opr) ASLA ASLB ASLD ASR (opr) ASRA ASRB
Logical Shifts LSL (opr) LSLA LSLB LSLD LSR (opr) LSRA LSRB LSRD
Rotates ROL (opr) ROR (opr) ROLA ROLB RORA RORB There is no rotate of D
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Example of use
Interesting data manipulation
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Example of use
Exchange the upper and lower nibbles of a byte in memory.
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Lecture summary
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Have covered The Logical instructions to perform Boolean
operations The Data Testing The Shift and Rotate instructions
Joanne E. DeGroat, OSU
Assignment
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Problems Chapter 3 page 87 Problem 19 Problem 21