; Title - Screen Display
; By    - Adam Trionfo
; Rev   - 1.1 - March 22, 2002
;         1.2 - November 30, 2003
;               * Made compatible with HVGLIB.H
; 
; This program could not have been written without using
; Mike White's "Astro BASIC 4x2 Multicart Loader" and
; and the "Nutting Manual" as a reference.
;
;  
; About this Program
; ------------------ 
;
; Displays four pixels (repeated four times) at $4000
; (the top-left of the screen).
; The byte value displayed is $B1, which should display
; color registers 0-3, but the order displayed is
; reverse from what I expect (3-0).  Why?
;
;
; Assembling this Program
; -----------------------
;    This file will assemble with ZMAC 1.3 (a little
; known, freely distributable Z-80 assembler (with C
; source), that has a 25-year history.  ZMAC can be
; compiled under just about any O.S. in existence, so
; try it out. 
;  
; To assemble Z-80 source code using ZMAC:
;  
; zmac -i -m -o <outfile> -x <listfile> <filename>
; 
; For example, to assemble this Astrocade Z-80 program:
;    
; zmac -i -m -o fourcolr.bin -x fourcolr.lst fourcolr.asm

INCLUDE "HVGLIB.H"      ; Home Video Game Library Header

        ORG    FIRSTC    ; First Byte of Cartridge
        DB     "U"       ; User Cartridge Sentinel

; Menu Selection Choice #1
        DW     MENUST   ; Next Menu Link
        DW     PRGNAM   ; Address of Program Name text
        DW     PRGST    ; Jump here if selected
 
; Program Start
PRGST:  DI                ; Disable interrupts

        SYSTEM (INTPC)    ; Start System Interpreter 

        DO     (SETOUT)   ; Set Display Ports
        DB     176D       ; Vertical Blanking Line 
        DB     44D        ; Left/Right Color Boundary 
        DB     $18        ; Interrupt Mode 

        DO     (COLSET)   ; Set Color Registers
        DW     COLTAB     ; Color Table

        DO     (FILL)     ; Screen Fill
        DW     $4000      ; Destination
        DW     4000D      ; Bytes to move
        DB     $00        ; Fill with zeros

        DO     (MOVE)     ; Move Bytes
        DW     $4000      ; Destination
        DW     4D         ; Bytes to move (four)
        DW     TOMOVE     ; Source Address

        EXIT              ; Exit System Interpreter

        EI                ; Enable interrupts 

LOOP:   NOP               ; Endless loop
        JP     LOOP       ; End of program

; Program Data

; Color Table #1
COLTAB: DB     $00        ; Color 0 Right - Black
        DB     $5A        ; Color 1 Right - Red
        DB     $86        ; Color 2 Right - Yellow
        DB     $F9        ; Color 3 Right - Blue
        DB     $00        ; Color 0 Left  - Black
        DB     $5A        ; Color 1 Left  - Red
        DB     $86        ; Color 2 Left  - Yellow
        DB     $F9        ; Color 3 Left  - Blue

; Program Name
PRGNAM: DB     'T','E','S','T'
        DB     $00        ; End of String

; Bytes to move
TOMOVE: DB     00011011B  ; Four pixels (0,1,2,3)
        DB     00011011B  ; Four pixels (0,1,2,3)
        DB     00011011B  ; Four pixels (0,1,2,3)
        DB     00011011B  ; Four pixels (0,1,2,3)

; End of Program