Re: reading vic20 or c64 column

From: Spiro Trikaliotis <*ml-cbmhackers_at_trikaliotis.net*> Date: Tue, 7 Jul 2015 20:52:58 +0200 Message-ID: <20150707185257.GA23439@hermes.local.trikaliotis.net> · ml-cbmhackers_at_trikaliotis.net

Hello,

* On Mon, Jul 06, 2015 at 10:13:23AM +0200 smf wrote:

> For example it's possible to enable all rows or all columns and then poll to
> see if any key is pressed (the commodore LCD rom actually does this).

The C64 does so, too, cf. iSCNKEY ($FF9F).

EA87 LDA #$00
... some code, A is not changed ...
EA90 STA $DC00  ; test all rows
EA93 LDX $DC01  ; get columns
EA96 CPX #$FF   ; nothing pressed?
EA98 BEQ $EAFB  ; yes --> Skip scanning the keyboard

It's the same code for the VIC20, only the addresses vary.

Regards,
Spiro.

-- 
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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