;****************************************************************
; 68705-P3 Device Equates for DASM,				*
;	Including notes on microcontroller layout.		*
;****************************************************************
; The P3 version of the 68705 is distributed in a small, 28 pin
; package, and thus lacks many of the features of the larger
; siblings of this particular micontrontroller.
; Memory is limited with 112 usable bytes of RAM and 1804 bytes 
; of EPROM. Note that addresses $000-$0FF may be accessed with a
; single byte "Page Zero" addressing mode (ala 6502).
;
; An abbreviated memory map is given below:
; *$000-$00F	I/O and Timer Hardware
; *$010-$07F	RAM (112 Bytes)
; *$080-$0FF	Page Zero EPROM
; *$100-$783	EPROM
; *$784 	Mask Option Register
; *$785-$7F7	Bootstrap ROM
; *$7F8-$7F9	Timer IRQ Vector
; *$7FA-$7FB	External IRQ Vector
; *$7FC-$7FD	SWI Vector (Think 'BRK')
; *$7FE-$7FF	Reset Vector
;****************************************************************
; Memory Layout							*
;****************************************************************
HARDWARE_BASE		EQU $000
RAM_START		EQU $010
RAM_END			EQU $07F

EPROM_ZEROPAGE		EQU $080
EPROM_USER		EQU $100
EPROM_MASKREG		EQU $784

MASKROM_BOOT		EQU $785

EPROM_IRQVecs		EQU $7F8
EPROM_TimerIRQV		EQU (EPROM_IRQVecs + 0)
EPROM_ExtIRQV		EQU (EPROM_IRQVecs + 2)
EPROM_SWIV		EQU (EPROM_IRQVecs + 4)
EPROM_ResetV		EQU (EPROM_IRQVecs + 6)
;****************************************************************
; I/O and Timer Hardware Equates				*
;****************************************************************
;**************
; General I/O *
;**************
; All data registers are R/W,
; Data direction registers are write only, (reads return 1)
; 0->input, 1->output

; Port A is an 8-Bit I/O port,
; Bits 7->0 map to pins 27->20 respectively. 
PortA_Data		EQU $000
PortA_DataDirection	EQU $004

; Port B is an 8-Bit I/O port,
; Bits 7->0 map to pins 19->12 respectively. 
PortB_Data		EQU $001
PortB_DataDirection	EQU $005

; Port B is a 4-Bit I/O port,
; Bits 3->0 map to pins 11->8 respectively.
; Bits 7->4 always read as "1" 
PortC_Data		EQU $002
PortC_DataDirection	EQU $006

;*****************
; Timer Hardware *
;*****************
; The structure of this register depends upon the
; setting of the "TOPT" bit in the Mask Option Register
;
;           7   6   5   4   3   2   1   0
; TOPT=1 : TIR TIM  1   1   1   1   1   1   
; TOPT=0 : TIR TIM TIN TIE PSC PS2 PS1 PS0
;
; TIR- Timer Interrupt Request
;	A '1' indicates a timer IRQ has occured,
;	write a zero here to clear it.
; TIM- Timer Interrupt Mask 
;	1=Masked,0=Unmasked
; TIN- Timer Input Select
;	1=External clock (pin 7)
;	0=Internal clock (CPU freq/4)
; TIE- External Timer Enable
;	1=Enable external timer pin 7
;	0=Disable
; PSC- Prescale Clear
;	Write 1 to reset prescaler,
;	reads return 0.
; PSx- Prescale Settings
;	PS2 PS1 PS0  Div
;	 0   0   0     1
;	 0   0   1     2
;	 0   1   0     4
;	 0   1   1     8
;	 1   0   0    16
;	 1   0   1    32
;	 1   1   0    64
;	 1   1   1   128
Timer_Control		EQU $009

; 8-Bit Down-Counter
; IRQ Fires when timer transitions to $00
; The timer continues to count after the IRQ has fired,
; (and the counter value rolled over to $FF), so if
; you need auto reload, it has to be done by hand.
Timer_Data		EQU $008
;****************************************************************
; "Special" Hardware Equates					*
;****************************************************************
; This thing is only important when
; copying data into the EPROM.
; Don't worry about it.
Programming_Control	EQU $00B

; This thing defines some post-reset states and
; general hardware configuration. It's located
; at the end of the EPROM so these values are "safe."
;
;  7   6    5   4   3   2   1   0 
; CLK TOPT CLS TIE     PS2 PS1 PS0
;
; CLK- Oscillator Type
;	1=Resistor Capacitor
;	0=Crystal
; TOPT- Timer Option
;	Controls the layout of the Timer Control
;	Register (see above description).
; CLS- Timer/Prescale Clock Source
;	1=External TIMER Pin
;	0=Internal Clock
; TIE- Timer External Enable
;	Sets the initial value of TIE
; PS2,PS1,PS0-
;	Initial values of the prescale regs.
Mask_Option		EQU $784