;
; Firmware for Ciarcia's Z8000 Trump Card boot ROM.
; Assembles online at asm80.com
;
; 2023-02-07 OCR'd from magazine page scan to create this file.
;
; "bucket" refers to the simple input buffer, which is a 2K RAM with a counter driving the address lines.
;
	.cpu	z80			; It isn't a z80, but you have to specify something.
;
; The Z8000 is little-endian.
; You need to split the output into odd and even bytes for two separate ROM chips.
; The Trump Card boots through an 8-bit PC bus interface.
; Which is well obsolete in 2023, you may be better off writing a boot ROM
; that boots through an FTDI USB FIFO interface module.
;
	.dw	$0000			;00	DW	$0000		; Reserved control word
	.dw	$D000			;02	DW	$D000		; Flag and control word
	.dw	$0000			;04 	DW	$0000		; Segment Register Segment Offset
	.dw	$000B			;06 	DW	$000B		; Set refresh freq and enable  

	.dw	$2100,$9E01		;08	LD R0, #%9E01		; Set refresh freq and enable 
	.dw	$1404,$0003,$0001	;0C	LDL RR4,#%0003 0001	; Set port addresses
	.dw	$7D0B			;12	LDCTL REFRESH, R0	; Load refresh value

	.dw	$3E40			;14	OUTB @R4, RH0		; Set R4 as reset-bucket port
	.dw	$3C40			;16	INB RH0, @R4		; Read bucket without increment 
	.dw	$A800			;18	INCB RH0, #1		; Increment input value
	.dw	$E6FC			;1A	JR 0 EQ,%0014		; Repeat if equal to 0

	.dw	$3C40			;1C	INB RH0, @R4		; Read bucket
	.dw	$8A80			;1E	CPB RH0, RL0		; Compare bucket value to 01
	.dw	$EFF9			;20	JR NC UGE, %0014	; Do again if not > 01

	.dw	$C803			;22	LDB RL0, #%03		; Load R0 with bucket available # 
	.dw	$3E58			;24	OUTB @R5, RL0		; Load bucket with R0
	.dw	$8400			;26	ORB RH0, RH0		; Set zero flag if RH0 is 0 
	.dw	$E6F5			;28	JR Z EQ,%0014		; Restart boot, else continue

	.dw	$3C52			;2A	INB RH2, @R5		; Read bucket and save in register 
	.dw	$3C53			;2C	INB RH3, @R5		; Read bucket and save in register 
	.dw	$3C5B			;2E	INB RL3, @R5		; Read bucket and save in register 
	.dw	$3C51			;30	INB RH1, @R5		; Read bucket and save in register 
	.dw	$3C59			;32	IND RL1, @R5		; Read bucket and save in register 
	.dw	$3A50,$0120		;34	INIRB @RR2, @R5 R1	; Read bucket into memory 
	.dw	$F013			;38	DBZNZ RH0		; Decrement RH0 and at 0 goto 0014

	.dw	$3E40			;3A	OUTB @R4, RH0		; Reset bucket
	.dw	$AB35			;3C	DEC R3, #6		; Decrement value in R3 six times
									; to set up first addr of code
	.dw	$1E28			;3E	JP @RR2			; Jump to loc defined in RR2