Using screen mode 2 in assembly

[l12n]

I'm trying to switch to screen mode 2 in assembly. I tried doing so by modifying registers 0 and 1, but all I get is a blank screen.

 

Or should I do it another way? I see the BIOS contains a MODE_1 function but no MODE_2.

[Tony Cruise]

I use the following settings for Screen mode 2:

 

 

WRITE_REGISTER:  EQU $1fd9

;
; Setup Screen 2,2
SETSCREEN2:
    LD BC,0002h	;Reg 0: Mode 2
    CALL WRITE_REGISTER
    LD BC,0206h        ; Name table 1800h
    CALL WRITE_REGISTER
    LD BC,03ffh        ; Colour table 2000h
    CALL WRITE_REGISTER
    LD BC,0403h        ; Pattern table 0000h
    CALL WRITE_REGISTER
    LD BC,0536h        ; Sprite attribute table 1b00h
    CALL WRITE_REGISTER
    LD BC,0607h        ; Sprite pattern table 3800h
    CALL WRITE_REGISTER
    LD BC,0700h        ; Base colours
    CALL WRITE_REGISTER
    LD BC,01c2h	;Reg 1: Mode 2, 16k, no interrupts, 16x16 sprites
    CALL WRITE_REGISTER
    RET

 

You then need to populate both the pattern and colour tables 3 x 256 x 8 and set the values in the name table (matching the pattern numbers you want to display).

[l12n]

Works great, thanks!

[artrag]

Mode 1 is already screen 2

I cannot understand the question...

[Tony Cruise]

On 6/1/2024 at 5:05 PM, artrag said:

Mode 1 is already screen 2

I cannot understand the question...

Yep you are indeed correct, but for someone looking at the TMS manual very confusing

[Captain Cozmos]

Tony's way is the easiest and strait forward but here is an alternative that I switched over to only because I had to reference the book so many times that I found it easier just to do it in binary.

 

GRAPHICS_MODE_2:               ; SET SCREEN MODE TO 32 COLUMN TEXT BY SENDING 16 BYTES TO THE VIDEO CONTROL PORT
    LD C, CTRL_PORT
    LD B, $10                          ; 16 BYTES
    LD HL, MODE_2_REGISTERS
    OTIR
RET

 

MODE_2_REGISTERS:
    DB %00000010, 128+0  ; REG 0: MODE 2
    DB %11000000, 128+1  ; REG 1: MODE 2, 16K, NO INTERRUPTS
    DB %00000110, 128+2  ; REG 2: NAME TABLE $1800
    DB %11111111, 128+3  ; REG 3: COLOR TABLE $2000
    DB %00000011, 128+4  ; REG 4: PATTERN TABLE $0000
    DB %00110110, 128+5  ; REG 5: SPRITE ATTRIBUTE TABLE $1B00
    DB %00000111, 128+6  ; REG 6: SRITE PATTERN TABLE $3800
    DB %11110000, 128+7  ; REG 7: BACKGROUND COLOR

 

 

TMS9928A.pdf

Edited June 18 by Captain Cozmos