DOS ain't dead - INT 10 - VIDEO - SET TEXT-MODE CURSOR SHAPE

Berlin, Germany,
13.02.2021, 21:58

INT 10 - VIDEO - SET TEXT-MODE CURSOR SHAPE (Developers)

Hi!

Int 10/AH=03h says: "A separate cursor is maintained for each of up to 8 display pages."
But specifying a display page (in BH) is not documented for Int 10/AH=01h.

Does anybody know, from his/her own experience (on hardware), if "Int 10/AH=01h" always works on the active/current page only?

(By the way: I'm not trying to control the shape itself, but the blinking/visibility via bits 5 & 6.)

Cheers,
Robert

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Forum admin

tkchia

14.02.2021, 13:15
(edited by tkchia, 14.02.2021, 13:59)

@ rr

INT 10 - VIDEO - SET TEXT-MODE CURSOR SHAPE

Post reply

Hello Robert,

> Does anybody know, from his/her own experience (on hardware), if "Int
> 10/AH=01h" always works on the active/current page only?

It seems that there is only one cursor shape, which is "shared" by all the different display pages.

The IBM BIOS data area keeps track of different cursor positions for each page (0x40:0x50--0x40:0x5f), but only one cursor shape (0x40:0x60--0x61).

(Also, I looked at the original IBM PC BIOS listings. Apparently there is really only one hardware cursor, at least on the CGA --- and when you switch the active display page (via int 0x10, ah = 5), the BIOS will actually move the cursor to the correct place, according to what 0x40:0x50 etc. says.)

ACT_DISP_PAGE PROC NEAR MOV ACTIVE_PAGE,AL ; SAVE ACTIVE PAGE VALUE MOV CX,CRT_LEN ; GET SAVED LENGTH OF REGEN BUFFER CBW ; CONVERT AL TO WORD PUSH AX ; SAVE PAGE VALUE MUL CX ; DISPLAY PAGE TIMES REGEN LENGTH MOV CRT_START,AX ; SAVE START ADDRESS FOR ; LATER REQUIREMENTS MOV CX,AX ; START ADDRESS TO CX SAR CX,1 ; DIVIDE BY 2 FOR 6845 HANDLING MOV AH,12 ; 6845 REGISTER FOR START ADDRESS CALL M16 POP BX ; RECOVER PAGE VALUE SAL BX,1 ; *2 FOR WORD OFFSET MOV AX,[BX+OFFSET CURSOR_POSN] ; GET CURSOR FOR THIS PAGE CALL M18 ; SET THE CURSOR POSITION JMP SHORT VIDEO_RETURN ACT_DISP_PAGE ENDP

Thank you!

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