Re: Does an enhanced //e _ALWAYS_ have 80 col. support?

[Don Bruder <dakidd@sonic.net>]

In article <Udzod.178761$df2.88821@edtnps89>,
 "Craig Bower \(Bender MX\)" <NOSPAMnitroacd@telusplanet.NAYSPAM.net> 
 wrote:

> "Oliver Schmidt" <ol.sc@web.de> wrote in message 
> news:cntq12$q8n$1@online.de...
> >But what I still don't understand: You say that all machines contain
> >the firmware. Does it mean that it is "visible" at $C300 even if
> >there's no card installed in the AUX slot?
> 
> Hi Oliver,
> 
> If you're looking to just use the mousetext characters, I'm pretty sure you 
> can
> set them to on without *any* 80-column card installed ... the following 
> excerpt
> is from the textfiles/apple site: "... you can get the functions of an 80 
> col card
> (save 80 col) with out the card. Just type: POKE 49162,0  then type: PR#3."
> 
> For Example from assembly:
> 
> LDA #$00                   Load Accum with #$00 (soft swtich bait)
> STA $C00A                Enable main ROM from $C300-$C3FF
> JSR $C300                  PR#3
> LDA #$00                   Reset Accum in case JSR $C300 scrambled it.
> <<STA $C00C>>    << Might be optional -try it with & w/out
> STA $C00F                Turn on Alternate character set.

ERROR! ERROR! ERROR! ERROR!!!

When playing with soft-switches, *ALWAYS* *READ* from them, unless 
specifically told that writing to activate them is OK. Some of them 
don't care. Others will toggle twice when written. (A read involves one 
access, a write involves two accesses - one to "locate" the address, the 
second to do the actual write) 

This gets really critical when playing with disk access or bank 
switching. You can blow the disk to the dark side of the moon by writing 
to a soft switch you're supposed to read, or vice-versa. The problem is 
that it isn't always clear which access method is right for a given soft 
switch - As mentioned, some trigger on a single (read) access, others 
trigger on a double (write) access, and others just don't care, so long 
as SOMETHING puts their address on the bus. The two most "dangerous" 
groups are the disk-acces switches, and the memory-related (bank 
switching) ones - As mentioned, it's easy to fry a disk by using an 
"STA" instead of an "LDA", or vice-versa. Likewise, several of the 
bank-switching addresses do two completely different things depending on 
whether you read from them or write to them when trying to set them up.  

Otherwise, the code looks good to me - Just turn the "STA <softswitch 
address>" lines into "LDA <softswitch address>", and it should be good 
to go.

> RTS                             Return from Subroutine.
> 
> And for reference, here's the softswitches involved
> 
> ROM SOFT SWITCHES
> 
> $C00A	W	SLOTC3ROMOFF	Enable main ROM from $C300-$C3FF
> $C00B	W	SLOTC3ROMON	Enable slot ROM from $C300-$C3FF
> 
> VIDEO SOFT SWITCHES
> 
> $C00C	W	80COLOFF	Turn off 80 column display
> $C00D	W	80COLON 	Turn on 80 column display
> $C00E	W	ALTCHARSOFF	Turn off alternate characters
> $C00F	W	ALTCHARSON	Turn on alternate characters
> 
> Best of luck,
> Craig 
> 
>

-- 
Don Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004.
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