;****************************************************************
; 68705P3 Clock							*
;****************************************************************
; A simple 24-hour clock using some 7-Segment displays		*
; and LEDs controlled by the 68705P3. A 74HC238 and UDN2981	*
; are required to assist the microcontroller. (See schematic)	*
;								*
; The time set operation operates as follows:			*
;	*Switches 0-3 choose the (binary) number to enter	*
;	*Switches 5-6 select the digit to modify-		*
;		56						*
;		00-Minutes, Ones				*
;		10-Minutes, Tens				*
;		01-Hours, Ones					*
;		11-Hours, Tens					*
;	*Switch 7 enters the digit (leave it down to change	*
;		things on the fly).				*
;								*
; Written by: Osman Celimli					*
;****************************************************************
	PROCESSOR 68705
	INCDIR	    "C:\MC68705"
	INCLUDE     "68705P3.asm"

	ORG HARDWARE_BASE	; Padding for programmer
	dc.b $FF		; format restrictions (2048x8)
;****************************************************************
; RAM Layout							*
;****************************************************************
	ORG RAM_START
Display_7Segs	ds.b 4
Display_Colon	ds.b 1
Display_LEDs	ds.b 3
Display_Current	ds.b 1

FrameCounter	ds.b 1

DownCount_Lo	ds.b 1 ; 
DownCount_Hi	ds.b 1 ; 625->0 Down Counter

Time_Set	ds.b 1

Set_Switches	ds.b 1
Set_Value	ds.b 1
Temp_Digit	ds.b 1
Temp_TOffset	ds.b 1
Temp_Ones	ds.b 1
Temp_Tens	ds.b 1

Time_Seconds	ds.b 1
Time_Minutes	ds.b 1
Time_Hours	ds.b 1

GLO_Temp	ds.b 1

	ECHO "RAM Left: ",(RAM_END-*)
;****************************************************************
; ZeroPage EPROM						*
;								*
;								*
;****************************************************************
	ORG EPROM_ZEROPAGE
;****************************************************************
; 7-Segment Digit Table						*
;****************************************************************
DigitTable dc.b $81,$CF,$92,$86,$CC,$A4,$A0,$8F,$80,$84
;****************************************************************
; Timer IRQ							*
;****************************************************************
;***************
; Seconds Tick *
;***************
DoSecondsTick	SUBROUTINE
	DEC Time_Seconds
	beq .MinutesTick
	rts
.MinutesTick
	LDA #60
	STA Time_Seconds
	LDA Time_Minutes
	INC
	STA Time_Minutes
	CMP #60
	beq .HoursTick
	rts
.HoursTick
	clr Time_Minutes
	LDA Time_Hours
	CMP #23
	bne .TickDone
	LDA #$FF
.TickDone
	INC
	STA Time_Hours
	rts
;********************
; Animation Updates *
;********************
DoAnimationUpdates	SUBROUTINE
	LDX FrameCounter
	LDA Anim_Sand_Hi,X
	STA Display_LEDs + 2
	LDA Anim_Sand_Mi,X
	STA Display_LEDs + 1
	LDA Anim_Sand_Lo,X
	STA Display_LEDs
	INX
	CPX #244
	bne .AnimDone
	LDX #0
.AnimDone
	STX FrameCounter
	rts
;**************************
; Main Display Update IRQ *
;**************************
; Note- Frequency is obtained by a 
; ((4Mhz Source Clock / 4 Pre-Prescaler) / 64 Prescaler) / 25 Down Count
; ~625Hz IRQ For Display Muxing.
; /625 for second accum.
Timer_IRQ	SUBROUTINE
	LDA #%00000110
	STA Timer_Control	; Clear IRQ
	LDA #25
	STA Timer_Data		; Reset down counter

	LDX Display_Current
	LDA Display_7Segs,X
	STX PortC_Data		; Swap LED Mux
	STA PortB_Data		; Update LED Data
	DEX
	bpl .WriteDisplOff
	LDX #7
.WriteDisplOff
	STX Display_Current

	DEC DownCount_Lo	; Update /625 Divisor
	bne .IRQBail
	LDA DownCount_Hi
	beq .DoUpdates
	DEC
	STA DownCount_Hi
.IRQBail
	rti
.DoUpdates			; We've ticked down 1 sec,
	LDA #>625		; Reset /625 divisor,
	STA DownCount_Hi	; accumulate hours, minutes, etc.
	LDA #<625		; and then update the seconds animation
	STA DownCount_Lo

	LDA Time_Set		; Do updates if we're not in time set mode
	beq .tick
	rti
.tick
	jsr DoSecondsTick
	jsr DoAnimationUpdates
	rti

	ECHO "Zero Page ROM Left: ",(EPROM_USER-*)
;****************************************************************
; Main User EPROM						*
;								*
;								*
;****************************************************************
	ORG EPROM_USER
;****************************************************************
; Start								*
;****************************************************************
Start	SUBROUTINE
	jsr BinTo7Seg
	jsr TimeSetMode
	bra Start
;****************************************************************
; Startup Initialization					*
;****************************************************************
MC68705_Init	SUBROUTINE
	sei
	RSP
; First, Zero all of RAM.
	LDX #(RAM_END-RAM_START)
.RAMClear
	clr RAM_START,X
	DEX
	bpl .RAMClear

; Now initialize the ports...
	LDA #0
	STA PortA_DataDirection ; Port A is input (Switches)
	LDA #$FF
	STA PortB_DataDirection ; Both Port B (LED Control) and
	STA PortC_DataDirection ; and Port C (LED Mux, Debug LED) are output
	LDA #00
	STA PortB_Data
	STA PortC_Data		; and are init'd to zero.

	LDA #12
	STA Time_Hours		; 12:00PM Start

	LDA #60
	STA Time_Seconds

	LDA #>625
	STA DownCount_Hi
	LDA #<625
	STA DownCount_Lo	; Initialize /625 Divisor

	LDA #25
	STA Timer_Data		; Set down counter
	LDA #%00001110
	STA Timer_Control	; Unmask IRQ, Reset Prescale, Start Timer.
	cli
	jmp Start
;****************************************************************
; Divide by 10 Routine						*
;****************************************************************
Div10AX	SUBROUTINE
; Divide the value in A by 10.
; Remainder in A, Result in X
	LDX #0
.acc
	CMP #10
	bmi .finished
	SUB #10
	INX
	bra .acc
.finished
	rts
;****************************************************************
; Binary -> 7 Segment Conversion Routine			*
;****************************************************************
BinTo7Seg	SUBROUTINE
	LDA Time_Minutes
	jsr Div10AX
	STA GLO_Temp

	LDA DigitTable,X
	STA Display_7Segs + 2		; Store Minutes Tens
	LDX GLO_Temp
	LDA DigitTable,X
	STA Display_7Segs + 3		; Store Minutes Ones

	LDA Time_Hours
	jsr Div10AX
	STA GLO_Temp

	LDA DigitTable,X
	STA Display_7Segs + 0		; Store Hours Tens
	LDX GLO_Temp
	LDA DigitTable,X
	STA Display_7Segs + 1		; Store Hours Ones
	rts
;****************************************************************
; Time Set							*
;****************************************************************
TimeSetMode	SUBROUTINE
; Switch Layout-
;
;  7   6   5   4   3   2   1   0
; SET SL1 SL0 VL4 VL3 VL2 VL1 VL0
;
; All switches are active (on) low.
;
; SET- Enable time set mode
; SL- Select digit for modification
; VL- Value to modify the digit to.
	LDA PortA_Data
	STA Set_Switches
	bpl .DoSetTime
	clr Display_Colon
	clr Time_Set
	rts
.DoSetTime
	LDA #$FF
	STA Display_Colon
	STA Time_Set

	LDA Set_Switches
	COM
	STA Set_Switches
	LSR
	LSR
	LSR
	LSR
	LSR
	COM
	AND #3
	TAX
	LDA Display_7Segs,X
	AND #$7F
	STA Display_7Segs,X
	TXA
	EOR #3
	STA Temp_Digit		; Store Digit Selection
	LSR
	STA Temp_TOffset
;Note-
; *Temp_Digit
;  -00 Minutes-Ones
;  -01 Minutes-Tens
;  -10 Hours-Ones
;  -11 Hours-Tens
;
; *Temp_TOffset
;  -0 Minutes
;  -1 Hours

	TAX
	LDA Time_Minutes,X
	jsr Div10AX
	STA Temp_Ones
	LDA TimeSet_TenTable,X
	STA Temp_Tens

	LDA Set_Switches	; Get the switch configuration from Port A
	AND #$0F
	CMP #9
	bmi .SwitchesInRange
	LDA #9
.SwitchesInRange
	STA Set_Value

	LDA Temp_Digit		; Are we checking tens or ones?
	AND #1
	bne .ProcessTens
.ProcessOnes
	LDX Temp_TOffset
	LDA Time_Minutes,X
	SUB Temp_Ones
	ADD Set_Value
	STA Time_Minutes,X
	bra .EnsureTimeCaps
.ProcessTens
	LDX Set_Value
	LDA TimeSet_TenTable,X
	STA Set_Value
	LDX Temp_TOffset
	LDA Time_Minutes,X
	SUB Temp_Tens
	ADD Set_Value
	STA Time_Minutes,X
.EnsureTimeCaps
	LDA Time_Minutes,X
	CMP TimeSet_CapTable,X
	bmi .CapsOK
	LDA TimeSet_CapSetTable,X
.CapsOK
	STA Time_Minutes,X
	rts

;**********************
; Tables for Time Set *
;**********************
TimeSet_TenTable dc.b 0,10,20,30,40,50,60,70,80,90
TimeSet_CapTable dc.b 60,24
TimeSet_CapSetTable dc.b 59,23

;****************************************************************
; Seconds Animation Table					*
;****************************************************************
; May as well just use a nice, (lazy) easy table to use up all that EPROM.
; You can replace this pattern with anything you like, really.
;
; This is kind of like a falling sand sort of thing.
;*************
; Segs 19-16 *
;*************
Anim_Sand_Hi	dc.b %11111111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111 ; 32


		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11110111,%11111011,%11111101,%11111110

		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11110111,%11111011 ; 64
		
		
		dc.b %11111101,%11111110,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11110111

		dc.b %11111011,%11111101,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11110111 ; 96


		dc.b %11111011,%11111101,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11110111,%11111011

		dc.b %11111101,%11111110,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11110111,%11111011,%11111101,%11111110 ; 128


		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111 ; 160


		dc.b %11110111,%11111011,%11111101,%11111110
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11110111,%11111011
		dc.b %11111101,%11111110,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11110111
		dc.b %11111011,%11111101,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11110111
		dc.b %11111011,%11111101,%11111110,%11111111 ; 192


		dc.b %11111111,%11111111,%11110111,%11111011
		dc.b %11111101,%11111110,%11111111,%11111111
		dc.b %11110111,%11111011,%11111101,%11111110
		dc.b %11111111,%11110111,%11111011,%11111101

		dc.b %11111110,%11110110,%11111010,%11111100
		dc.b %11110100,%11111000,%11110000,%11110000
		dc.b %11110000,%11110000,%11110000,%11110000
		dc.b %11110000,%11110000,%11110000,%11110000 ; 224


		dc.b %11111000,%11111100,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11111111 ; 244

;*************
; Segs 15-08 *
;*************
Anim_Sand_Mi	dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%01111111,%10111111,%11011111
		dc.b %11101111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%01111111,%10111111,%11011111 ; 32


		dc.b %11101111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %01111111,%10111111,%11011111,%11101111
		dc.b %11110111,%11111011,%11111101,%11111110
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111 ; 64


		dc.b %11111111,%11111111,%01111111,%10111111
		dc.b %11011111,%11101111,%11110111,%11111011
		dc.b %11111101,%11111110,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%01111111
		dc.b %10111111,%11011111,%11101111,%11110111
		dc.b %11111011,%11111101,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111 ; 96


		dc.b %11111111,%11111111,%11111111,%01111111
		dc.b %10111111,%11011111,%11101111,%11110111
		dc.b %11111011,%11111101,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%01111111,%10111111
		dc.b %11011111,%11101111,%11110111,%11111011
		dc.b %11111101,%11111110,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111 ; 128


		dc.b %01111111,%10111111,%11011111,%11101111
		dc.b %11110111,%11111011,%11111101,%11111110
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%01111111,%10111111,%11011111

		dc.b %11101111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111110,%11111110,%11111110
		dc.b %11111110,%01111110,%10111110,%11011110
		dc.b %11101110,%11110110,%11111010,%11111100 ; 160


		dc.b %11111100,%11111100,%11111100,%11111100
		dc.b %01111100,%10111100,%11011100,%11101100
		dc.b %11110100,%11111000,%11111000,%11111000
		dc.b %11111000,%11111000,%01111000,%10111000

		dc.b %11011000,%11101000,%11110000,%11110000
		dc.b %11110000,%11110000,%11110000,%01110000
		dc.b %10110000,%11010000,%11100000,%11100000
		dc.b %11100000,%11100000,%11100000,%01100000 ; 192


		dc.b %10100000,%11000000,%11000000,%11000000
		dc.b %11000000,%11000000,%01000000,%10000000
		dc.b %10000000,%10000000,%10000000,%10000000
		dc.b %00000000,%00000000,%00000000,%00000000

		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000 ; 224

		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %10000000,%11000000,%11100000,%11110000
		dc.b %11111000,%11111100,%11111110,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111

		dc.b %11111111,%11111111,%11111111,%11111111 ; 244

;*************
; Segs 07-00 *
;*************
Anim_Sand_Lo	dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%11111111,%11111111,%11111111
		dc.b %11111111,%01111111,%10111111,%11011111

		dc.b %11101111,%11110111,%11111011,%11111101
		dc.b %11111110,%11111110,%11111110,%11111110
		dc.b %11111110,%11111110,%11111110,%11111110
		dc.b %11111110,%11111110,%11111110,%11111110 ; 32


		dc.b %11111110,%11111110,%11111110,%11111110
		dc.b %11111110,%01111110,%10111110,%11011110
		dc.b %11101110,%11110110,%11111010,%11111100
		dc.b %11111100,%11111100,%11111100,%11111100

		dc.b %11111100,%11111100,%11111100,%11111100
		dc.b %11111100,%11111100,%11111100,%11111100
		dc.b %01111100,%10111100,%11011100,%11101100
		dc.b %11110100,%11111000,%11111000,%11111000 ; 64


		dc.b %11111000,%11111000,%11111000,%11111000
		dc.b %11111000,%11111000,%11111000,%11111000
		dc.b %11111000,%11111000,%01111000,%10111000
		dc.b %11011000,%11101000,%11110000,%11110000

		dc.b %11110000,%11110000,%11110000,%11110000
		dc.b %11110000,%11110000,%11110000,%11110000
		dc.b %11110000,%11110000,%11110000,%01110000
		dc.b %10110000,%11010000,%11100000,%11100000 ; 96


		dc.b %11100000,%11100000,%11100000,%11100000
		dc.b %11100000,%11100000,%11100000,%11100000
		dc.b %11100000,%11100000,%11100000,%01100000
		dc.b %10100000,%11000000,%11000000,%11000000

		dc.b %11000000,%11000000,%11000000,%11000000
		dc.b %11000000,%11000000,%11000000,%11000000
		dc.b %11000000,%11000000,%01000000,%10000000
		dc.b %10000000,%10000000,%10000000,%10000000 ; 128

		dc.b %10000000,%10000000,%10000000,%10000000
		dc.b %10000000,%10000000,%10000000,%10000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000

		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000 ; 160


		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000

		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000 ; 192


		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000

		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000 ; 224



		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %00000000,%00000000,%00000000,%00000000
		dc.b %10000000,%11000000,%11100000,%11110000

		dc.b %11111000,%11111100,%11111110,%11111111 ; 244

;****************************************************************
; Dummy IRQ							*
;****************************************************************
Dummy_IRQ	SUBROUTINE
	rti
	ECHO "User EROM Left: ",(EPROM_MASKREG-*)
;****************************************************************
; Mask Option Regs						*
;****************************************************************
	ORG EPROM_MASKREG
; Crystal Clock, Software Timer
; Internal Clock Timer Source, External Timer Disable
; and Prescale setting of /64.
MaskReg_Setting	dc.b %00000110
;****************************************************************
; IRQ Vectors							*
;****************************************************************
	ORG EPROM_IRQVecs
TimerIRQVec	dc.w Timer_IRQ
ExtIRQVec	dc.w Dummy_IRQ
SWIRQVec	dc.w Timer_IRQ
ResetVec	dc.w MC68705_Init