ECE 265 – LECTURE 7 The M68HC11 Basic Instruction Set Logical, Shift and Rotate, Data Testing 8/14/ ECE265

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. 8/14/ ECE265

The Logical Instructions  Instructions to perform Boolean operations on data  Instructions for AND NOT and OR operation 8/14/2015ECE265 3

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? 8/14/2015ECE265 4

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  AND-ed with  giving /14/2015ECE265 5

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? 8/14/2015ECE265 6

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? 8/14/2015ECE265 7

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) 8/14/2015ECE265 8

Examples  Example instructions Accum A has val $1C Memory $D330 val $2F  (a) ANDA $D330  (b) EORA $D330  (c) ORAA $D330 8/14/2015ECE265 9

Data Testing Instructions  Will cover the Bit Test and Setting and Clearing of bits.  The branch will be covered with branches. 8/14/2015ECE265 10

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 8/14/2015ECE265 11

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. 8/14/2015ECE265 12

Shift and Rotate Instructions  The instructions perform arithmetic and logical shifts and also rotate the data. 8/14/2015ECE265 13

The effect of shift and rotates  What do the instructions do? 8/14/2015ECE265 14

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 8/14/2015ECE265 15

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 8/14/2015ECE265 16

Example of use  Interesting data manipulation 8/14/2015ECE265 17

Example of use  Exchange the upper and lower nibbles of a byte in memory. 8/14/2015ECE265 18

Lecture summary 8/14/2015ECE  Have covered  The Logical instructions to perform Boolean operations  The Data Testing  The Shift and Rotate instructions

Assignment 8/14/2015ECE  Problems Chapter 3 page 87  Problem 19  Problem 21