tableSearch.asm

; tableSearch.asm
;
; Created: 21/07/2018 6:49:15 PM
; Author : Glenn Matthews
;

; Define here the variables
.def	temp  =r16
.def	small =r17
.def	high_val  =r19
.def	high_location  =r20

; Define here Reset and interrupt vectors, if any
; the only one at the moment is the reset vector
;that points to the start of the program (i.e., label: start)
reset:
   rjmp start
   reti      ; Addr $01
   reti      ; Addr $02
   reti      ; Addr $03
   reti      ; Addr $04
   reti      ; Addr $05
   reti      ; Addr $06        Use 'rjmp myVector'
   reti      ; Addr $07        to define a interrupt vector
   reti      ; Addr $08
   reti      ; Addr $09
   reti      ; Addr $0A
   reti      ; Addr $0B        This is just an example
   reti      ; Addr $0C        Not all MCUs have the same
   reti      ; Addr $0D        number of interrupt vectors
   reti      ; Addr $0E
   reti      ; Addr $0F
   reti      ; Addr $10

; Program starts here after Reset
.cseg
start:		; start here

; The Z register is used as a pointer to the t  entries in the table 
; so we need to load the location of the table into the high and 
; low byte of Z. 
; Note how we use the directives 'high' and 'low' to do this.

	LDI ZH, high(Tble<<1)	; Initialize Z-pointer
	LDI ZL, low(Tble<<1)	; a byte at a time  (why <<1?)

	LDI small, $FF			; Smallest value (small)
	LDI r18, $00			; Loop conditional
	LDI r19, $00			; Highest Value (high)
	LDI r20, $00			; Location of Highest Value (high_location)

loop:
	; ------- Small value 
	LPM temp, Z ; Load constant from table in memory pointed to by Z (r31:r30)
	CP temp, small
	BRLO change
	; ------- end

	; ------- High Value
	CP high_val, temp
	BRLO higher
	; ------- end

	INC r18 ; sets up 'for' loop
	CPI r18, $40
	BREQ here


	INC ZL 		; move the array pointer

; Note here that we only increment and compare the lower byte
; (very risky - why risky?).

	CPI ZL, low(Tble+64<<1) ;Tble+64 is one past the final entry
	BRNE loop

change:
	MOV small, temp
   jmp loop

higher:
	MOV high_val, temp
	MOV high_location, ZL
	jmp loop

here:
	jmp here	; this is required to imitate how the design would operate in real life

; Create 64 bytes in code memory of table to search.
; The DC directive defines constants in (code) memory
; you will search this table for the desired entry.
Tble:
  .DB   33,  85, 134, 215, 211,  22,  74,  41
  .DB   28, 185, 167,  70, 243, 162, 185, 137
  .DB  133,  25, 213,  18,  47, 159,  72, 134
  .DB    5,  76,  38, 246,  52, 150, 213, 202
  .DB   49, 149, 167, 212,  35,  59,  45,  25
  .DB  163,  50, 193,  20, 238,   6, 253,  73
  .DB   64, 192,  16,   6, 250,   4, 127, 229
  .DB    3, 113,  32,  77, 174,  15,  72,  13

.exit