;S2R0010B.Z80 -- Small Z80 Board, Bootstrap Loader
;
;Created: 29 JAN 1998
;Author: Douglas Beattie Jr.
;
NMIVEC	EQU	0066H		;Z80 NMI vector
MEMBOT	EQU	0800H		;Base of RAM memory
MEMTOP	EQU	1000H		;End of 2K, Out of memory
MEMSIZ	EQU	MEMTOP-MEMBOT
	.IF	(MEMSIZ .GT. 2048)
	.ERROR	"Memory Size too large."
	.ENDIF
;
; Note that the PIO decode uses A0 connected to C/D pin
;   and A1 connected to Port-select pin.  This is in
;   contradiction with convention, but optimizes code
;   for use in our application; where only one port will
;   be extensively used in any ISR.
;
PIO0	EQU	88H		;Base port addr, PIO #0 decode
PIO1	EQU	80H		;PIO #1 not currently implemented
P0DTAA	EQU	PIO0+0		;Port A data
P0CTLA	EQU	PIO0+1		;Port A control
P0DTAB
P0CTLB
;
	ORG	MEMBOT
RST0	DS	4	;4 bytes, allows for 'DI' opcode
RST1	DS	4
RST2	DS	4
RST3	DS	4
RST4	DS	4
RST5	DS	4
RST6	DS	4
RST7	DS	4
;
	ASEG			;Absolute Code Segment
	ORG	0000H		;Base of ROM
	JP	ENTRY		;Jump to Cold Boot
	ORG	0008H		;Restart vector @ 0008h
	JP	RST1
;
	ORG	0038H
	EXX
	LD	HL,(RST7VEC)
	PUSH	HL
	EXX
	RET
;
;	Initialize a PIO
;	port address of PIO is in Reg C
;
INITPIO LD	A,01001100B
	OUT	(C),A
	RET
;
;	Entry from Cold Boot or Restart @ 0
;
ENTRY	DI			;disable interrupts
	LD	SP,MEMTOP-1	;init stack ptr
	LD	C,P0CTLA	;set port addr
	CALL	INITPIO		;go init PIO0
	LD	HL,INTSERV	;point to ISR
	LD	(RST7VEC),HL
	IM	1
	EI
	HALT
	RST	1
	RET
;

	END	ENTRY



;Thu Jan 29 19:24:07 PST 1998
;Fri Jan 30 22:16:38 PST 1998