;
; Whippleway Experiment 9 for the ATmega328
;
; Created: 3/28/2017 8:06:37 PM
; Author : Dick Whipple
;
; Add Immediate Macro
;
.macro addi
    subi    @0, -@1          ;subtract the negative of an immediate value
.endmacro
;
start:
	ldi		r16,0b00000000		;set all bits of port b to input
	out		ddrb,r16
	ldi		r16,0b11111111		;turn on pull-up resistors on all bits of portb
	out		portb,r16
	ldi		r16,0b00000000		;set all bits of port c to input
	out		ddrc,r16
	ldi		r16,0b11111111		;turn on pull-up resistors on all bits of port c
	out		portc,r16
	ldi		r16,0b11111111		;set all bits of port d to output
	out		ddrd,r16
;
    jmp		exmp4_1 			;TARGET JUMP - Change try different examples.
;
; Experiment 4 Example 1 - Basic I/O
;
; Using IN and OUT instructions
;
; Set sense switches to 0b00xxxxxx (any one or more x's set and all others closed)
;
; Data LEDs display complement pattern
;
; Note: (1) Bits 0 to 5 of portb connect directly to senses switches 1 to 6. Sense switches 7 and 8 are connected
; to bits 1 and 2 of portc.  (2) When inputting sense switch portb directly, "up" produces cleared (0) bit while "down" a 
; set (1) bit.
;
exmp4_1:
	in	     r16,pinb		    ;get lower six bits of sense switches
	out		 portd,r16			;update LEDs 
	rjmp     exmp4_1
;
; Experiment 4 Example 2 - Two Way Selection (mask condition)
;
; Setting sense switch bit 7 = 1 displays a one (true) in Data LEDs.  Otherwise, zero (false) is displayed.
;
exmp4_2:
	call	  ssinp				;get sense switches into R16
	andi	  r16,0b10000000	;mask r16 to test bit 7
	brne	  exmp4_2_true		;if r16 bit 7 = 1, branch to true sequence
;
; False sequence
;
	ldi		  r16,0			    ;load zero (false) in r16
	rjmp      exmp4_2_exit		;branch to exit
;
; True sequence
;
exmp4_2_true:
	ldi		  r16,1				;load one (true) in r16
;
; Exit
;
exmp4_2_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_2			;repeat
;
; Experiment 4 Example 3a - One Way Selection (mask condition)
;
; Sense switch bit 7 = 1 will produce a one (true) in Data LEDs
;
exmp4_3a:
	call	  ssinp				;get sense switches into R16
	andi	  r16,0b10000000	;mask r16 to test bit 7
	ldi		  r16,0				;preload r16 with zero (false)
	breq	  exmp4_3a_exit		;if r16 bit 7 = 0, branch to exit
;
; True sequence
;
	ldi		  r16,1			    ;load one (true) in r16
;
; Exit
;
exmp4_3a_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_3a			;repeat
;
; Experiment 4 Example 3b - One Way Selection (mask condition using skip instruction)
;
; Sense switch bit 7 = 1 will produce a one (true) in Data LEDs
;
; Reads I/O port c pin (bit) 1 directly.  Recall that Sense Switch 7 up produces a zero on portc bit 1
;.
exmp4_3b:
	ldi		  r16,0				;preload r16 with zero (false)
	sbis	  pinc,1			;if portc pin (bit) 1 = 1 (sense switch down), branch to exit
;
; True sequence
;
	ldi		  r16,1			    ;load one (true) in r16
;
; Exit
;
exmp4_3b_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_3b			;repeat
;
; Experiment 4 Example 4a - Two Way Selection (unsigned comparison)
;
; Any sense switch input equal or greater than 120Q will produce a one (true)
;
exmp4_4a:
	call	  ssinp				;get sense switches into R16
	cpi		  r16,80			;compare r16 to 80 (r16 - 80)
	brsh	  exmp4_4a_true		;if r16 >= 80 branch to true sequence
;
; False sequence
;
	ldi		  r16,0			    ;zero (false) -> r16
	rjmp      exmp4_4a_exit		;branch to exit
;
; True sequence
;
exmp4_4a_true:
	ldi		  r16,1				;one (true) -> r16
;
; Exit
;
exmp4_4a_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_4a			;repeat
;
; Experiment 4 Example 4b - Two Way Selection (signed comparison)
;
; Try these sense switch settings:  (1) 000Q =  0 >= -80	LEDs = 1 (True)
;									(2) 261Q = -79 >= -80	LEDs = 1 (True)
;									(3) 260Q = -80 >= -80	LEDs = 1 (True)
;									(4) 257Q = -81 < -80	LEDs = 0 (False)
;
exmp4_4b:
	call	  ssinp				;get sense switches into R16
	cpi		  r16,-80			;compare r16 to 80 (r16 - 80)
	brge	  exmp4_4b_true		;if r16 >= 80 branch to true sequence
;
; False sequence
;
	ldi		  r16,0			    ;zero (false) -> r16
	rjmp      exmp4_4b_exit		;branch to exit
;
; True sequence
;
exmp4_4b_true:
	ldi		  r16,1				;one (true) ->r16
;
; Exit
;
exmp4_4b_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_4b			;repeat
;
; Experiment 4 Example 4c - One Way Selection (unsigned comparison)
;
; Any sense switch input less than 80 will produce a zero (false)
;
exmp4_4c:
	call	  ssinp				;get sense switches into R16
	cpi		  r16,80			;compare r16 to 80 (r16 - 80)
	ldi		  r16,0				;preload r16 with zero (false)
	brlo	  exmp4_4c_exit		;if r16 < 80 branch to exit
;
; True sequence
;
	ldi		  r16,1			    ;load r16 with one (true)
;
; Exit
;
exmp4_4c_exit:
	call	  LEDout
	rjmp	  exmp4_4c			;repeat
;
; Experiment 4 Example 5 - One Way Selection (arithmetic comparison - unsigned)
;
; Display the larger of 120 (170Q) and the value in the sense switches
;
exmp4_5:
	ldi		  r17,120			;load r17 with 120
	call	  ssinp				;load r16 with sense switch value
	cp		  r17,r16			;compare r17 to r16 (120 - r16)
	brlo	  exmp4_5_exit		;if r16 < 80 branch to exit
;
; True sequence - Switch registers
;
	mov		  r1,r16			;r16 -> r1 (temporary register)
	mov		  r16,r17			;r17 -> r16
	mov		  r17,r1		    ;r1 -> r17
;
; Exit
;
exmp4_5_exit:
	call	  LEDout			;display r16 in Data LEDs
	rjmp	  exmp4_5			;repeat
;
; Experiment 4 Example 6 - One Way Selection
;
; Convert the low nibble of the sense switches from hex to ASCII
;
exmp4_6:
	call	  ssinp				;load r16 with sense switch value
	andi	  r16, 0x0f			;mask off upper nibble
	addi	  r16,48			;assume 0 to 9 and add 48 ASCII bias
	cpi		  r16,57			;if r16 < 57, branch to exit
	brlo	  exmp4_6_exit
;
; True sequence
;
	addi	  r16,7				;add additional 7 ASCII bias for 10 to 15
;
; Exit
;
exmp4_6_exit:
	call	  LEDout			;display r16 in Data LEDs
                                ;0000 - ASCII 0 or 060Q to 1001 - ASCII 9 or 101Q
                                ;1010 - ASCII A or 101Q to 1111 - ASCII F or 106Q
	rjmp	  exmp4_6			;repeat
;
;	LED Output Subroutine
;
;	Outputs r16 to Data LEDS
;
;	Registers Used: r5,r16
;
LEDout:
	in		r5,pinc				;check status register button
	sbrs	r5,2				;if set, skip next instruction
	in		r16,sreg			;otherwise replace contents of r16 with status register
	out		portd,r16			;output r16 to port d
	ret
;
;	Sense Switch Input
;
;	Inputs Sense Switches to r16
;
;	Registers Used: r5,r16,sreg
;
;	Note. (1) Uses 6 bits of portb (bits 0 to 5) and 2 bits of portc (bits 0 to 1) (2) "Up" produces a set bit awhile "down" produces a cleard bit.
;
ssinp:
	in		r16,pinb			;get bits from port b into r16
	andi	r16,0x3f			;mask of bits 6 and 7
	mov		r5,r16				;move r16 to r5
	in		r16,pinc			;get bits from port c into r16
	andi	r16,0b00000011		;mask of bit 2 to 6
	clc							;clear carry
	ror		r16					;rotate r16 right 3 times to get bits 0 and 1 into bits 6 and 7
	ror		r16
	ror		r16
	or		r16,r5				;or r5 with r16 to merge the bits into r16
	com		r16					;complement to correct for switch configuration
	ret
;
;	2 Second Delay
;
;	Registers Used: r29,r30,r31
;
delay:
	ldi		r29,120			;use r29 to control number of full 16-bit count downs
loop:
	sbiw	r30,1			;count down combined r30:r31 registers to zero
	brne	loop			;if not zero, repeat count down
	dec		r29				;decrement r29 until zero
	brne	loop			;if not zero, count down r30:r31 again.
	ret						;done and return