;-------------------------------------------------------------------------------
; MSP430 Assembler Code Template for use with TI Code Composer Studio
;
;
;-------------------------------------------------------------------------------
            .cdecls C,LIST,"msp430.h"       ; Include device header file

;-------------------------------------------------------------------------------
            .def    RESET                   ; Export program entry-point to
                                            ; make it known to linker.
;-------------------------------------------------------------------------------
            .text                           ; Assemble into program memory.
            .retain                         ; Override ELF conditional linking
                                            ; and retain current section.
            .retainrefs                     ; And retain any sections that have
                                            ; references to current section.

;-------------------------------------------------------------------------------
RESET       mov.w   #__STACK_END,SP         ; Initialize stackpointer
StopWDT     mov.w   #WDTPW|WDTHOLD,&WDTCTL  ; Stop watchdog timer


;-------------------------------------------------------------------------------
; Main loop here
;-------------------------------------------------------------------------------

;ports are set as input on start so we don't need to set port 2 for hexes
init	BIS.B #0FFh,&P3DIR	;set port 3 as output
		CLR.B &P3OUT
		CLR R9
		CLR R5

		MOV.B #00Ah, &P1IE	;set port 1 as interrupt + input
		MOV.B #00Ah, &P1IES

		;R5 - state of the counter
		;R6 - button state
		;R7 - loop counter
		;R8 - flag that two buttons were pressed at the same time on load (so ignore clk later)
main
			CLR.B &P1IFG
			BIS #GIE+CPUOFF+SCG1+SCG0, SR
			MOV.B #00Ah, &P1IE ;enable interrupts


mainloop
			MOV.B &P1IN, R6
			BIT.B #08h, R6 ;check if the load button was clicked
			JZ load
			CMP #01h, R8
			MOV.B #0, R8	;reset the flag
			JZ main		;there was a load but it's not anymore, so go to sleep
			BIT.B #02h, R6 ;just in case test if clock was pressed
			JNZ main		;not zero - not pressed

jittersetup
			MOV.W #007FFh, R7 ;set the loop counter
			BIS #GIE, SR 	;enable interrupts

jitterloop
			DEC.W R7		;2 cycles
			MOV.B &P1IN, R6 ;3 cycles
			BIT #08h, R6	;2 cycles
			JZ load			;2 cycles
			BIT #02h, R6    ;test the clock input - we know "on" is "0" 2 cycles
			JNZ main	;if it was 1, go to sleep 2 cycles
			CMP.W #0, R7		;if we got to 2 cycles
			JNZ jitterloop	;2 cycles

decrease
			BIC #GIE, SR	;disable interrupts
			BIT.B #01h, R8 ;check if the load button was clicked in the meanwhile
			JNZ load ;otherwise, clock was clicked
			DEC.B R5		;decrease, set out and go to sleep
			MOV.B R5, &P3OUT
			JMP main

load
			MOV.B &P2IN, R5 ;move the values set by the user
			MOV.B R5, &P3OUT
			CLR R8
			OR #0F5h, R6
			CMP #0F5h, R6
			JNZ mainloop
is_two
			MOV.B #1, R8	;flag that there was a load
			JMP	mainloop ;load is enabled by value, not edge, so check it again

PORT1_ISR
			MOV.B &P1IN, R6 ;set the button state to the register
			CLR.B &P1IFG ;clear the interrupt flags
			BIC #GIE+CPUOFF+SCG1+SCG0, 0(SP) ;wake up the cpu
			RETI

;-------------------------------------------------------------------------------
; Stack Pointer definition
;-------------------------------------------------------------------------------
            .global __STACK_END
            .sect   .stack

;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  RESET
            .sect	".int04"
            .short	PORT1_ISR