; This is a "Hello World" program for Z80 and TMS9918 / TMS9928 / TMS9929 /
; V9938 or V9958 VDP.
; That means that this should work on SVI, MSX, Colecovision, Memotech,
; and many other Z80 based home computers or game consoles.
;
; Because we don't know what system is used, we don't know where RAM
; is, so we can't use stack in this program.
;
; This version of Hello World was written by Timo "NYYRIKKI" Soilamaa
; 17.10.2001
;
;----------------------------------------------------------------------
; Configure this part:

DATAP: EQU #98 ; VDP Data port #98 works on all MSX models
; (TMS9918/TMS9929/V9938 or V9958)
; #80 works on SVI 
; (for other platforms you have to figure this out by your self)

CMDP: EQU #99 ; VDP Command port #99 works on all MSX models
; (TMS9918/TMS9929/V9938 or V9958)
; #81 works on SVI
; (for other platforms you have to figure this out by your self)
;-----------------------------------------------------------------------
; Program starts here:

ORG 0 ; Z80 starts always from here when power is turned on
DI ; We don't know, how interrupts works in this system, so we disable them.

; Let's set VDP write address to #0000
XOR A
OUT (CMDP),A
LD A,#40
OUT (CMDP),A

; Now let's clear first 16Kb of VDP memory
LD B,0
LD HL,#3FFF
LD C,DATAP
CLEAR:
OUT (C),B
DEC HL
LD A,H
OR L
NOP ; Let's wait 8 clock cycles just in case VDP is not quick enough.
NOP
JR NZ,CLEAR

; Now it is time to set up VDP registers:
;----------------------------------------
; Register 0 to #0
;
; Set mode selection bit M3 (maybe also M4 & M5) to zero and 
; disable external video & horizontal interrupt
LD C,CMDP
LD E,#80

OUT (C),A
OUT (C),E
;---------------------------------------- 
; Register 1 to #50
;
; Select 40 column mode, enable screen and disable vertical interrupt

LD A,#50
INC E
OUT (C),A
OUT (C),E
;---------------------------------------- 
; Register 2 to #0
;
; Set pattern name table to #0000

XOR A
INC E
OUT (C),A
OUT (C),E
;---------------------------------------- 
; Register 3 is ignored as 40 column mode does not need color table
;
INC E
;---------------------------------------- 
; Register 4 to #1
; Set pattern generator table to #800

INC A
INC E

OUT (C),A
OUT (C),E
;---------------------------------------- 
; Registers 5 (Sprite attribute) & 6 (Sprite pattern) are ignored 
; as 40 column mode does not have sprites

INC E
INC E
;---------------------------------------- 
; Register 7 to #F0
; Set colors to white on black

LD A,#F0
INC E
OUT (C),A
OUT (C),E
;----------------------------------------

; Let's set VDP write address to #808 so, that we can write
; character set to memory
; (No need to write SPACE it is clear char already)
LD A,8
OUT (C),A
LD A,#48
OUT (C),A

; Let's copy character set
LD HL,CHARS
LD B, CHARS_END-CHARS
COPYCHARS:
LD A,(HL)
OUT (DATAP),A
INC HL
NOP ; Let's wait 8 clock cycles just in case VDP is not quick enough.
NOP
DJNZ COPYCHARS

; Let's set write address to start of name table
XOR A
OUT (C),A
LD A,#40
OUT (C),A

; Let's put characters to screen
LD HL,ORDER
LD B,ORDER_END-ORDER
COPYORDER:
LD A,(HL)
OUT (DATAP),A
INC HL

JR OVERNMI
NOP
NOP

; Here is address #66, that is entry for NMI
RETN ;Return from NMI

OVERNMI:
DJNZ COPYORDER

; The end
HALT

; Character set:
; --------------
ORDER:
DEFB 1,2,3,3,4,0,5,4,6,3,7
ORDER_END:

CHARS:

; H
DEFB %10001000
DEFB %10001000
DEFB %10001000
DEFB %11111000
DEFB %10001000
DEFB %10001000
DEFB %10001000
DEFB %00000000
; e
DEFB %00000000
DEFB %00000000
DEFB %01110000
DEFB %10001000
DEFB %11111000
DEFB %10000000
DEFB %01110000
DEFB %00000000
; l
DEFB %01100000
DEFB %00100000
DEFB %00100000
DEFB %00100000
DEFB %00100000
DEFB %00100000
DEFB %01110000
DEFB %00000000
; o
DEFB %00000000
DEFB %00000000
DEFB %01110000
DEFB %10001000
DEFB %10001000
DEFB %10001000
DEFB %01110000
DEFB %00000000
; W
DEFB %10001000
DEFB %10001000
DEFB %10001000
DEFB %10101000
DEFB %10101000
DEFB %11011000
DEFB %10001000
DEFB %00000000

; r
DEFB %00000000
DEFB %00000000
DEFB %10110000
DEFB %11001000
DEFB %10000000
DEFB %10000000
DEFB %10000000
DEFB %00000000
; d
DEFB %00001000
DEFB %00001000
DEFB %01101000
DEFB %10011000
DEFB %10001000
DEFB %10011000
DEFB %01101000
DEFB %00000000
chars_end: