Posted By
Superglob
on 2021-05-17
23:49:41
|  Chip Selects for Plus 4 an C16?
Hey everyone!
Anyone know what they're supposed to page in? There are also two undefined ones.. Any info / links to docs would be great
Thanks!
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Posted By
gerliczer
on 2021-05-18
02:26:37
| Re: Chip Selects for Plus 4 an C16?
Yes, there are people who know what they are supposed to page in. I'm not sure what you mean by undefined, but I do have a guess what those could be. You could find yourself the relevant documentation if you would be willing to exert any effort. Best place to start the search would be Bo Zimmerman's site if you still need a recommendation.
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Posted By
siz
on 2021-05-18
03:29:16
| Re: Chip Selects for Plus 4 an C16?
Could you please define what chip selects are you talking about? You mean the ones on the expansion port?
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Posted By
unclouded
on 2021-05-19
17:04:02
| Re: Chip Selects for Plus 4 an C16?
Do you mean the U16 outputs in the bottom right hand corner here? It wasn't clear to me straight away that 'SCS' refers to the speech module. Does anyone know what "SCS" stands for specifically? Speech Chip Select?
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Posted By
Superglob
on 2021-05-19
21:35:39
| Re: Chip Selects for Plus 4 an C16?
Found it in an earlier post (my bad)
CS0 = ROM low access ($8000-$bfff)
CS1 = ROM high access $(c000-fcff)
So basically allows you to split up the rom into two 16k segments. I'm *assuming* (always bad) that there are some pins to switch out the rom so you can have 48k or more going from $4000-$fcff like carts and what not but there's really little to go on as most of it is plus 4..
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Posted By
gerliczer
on 2021-05-20
01:31:45
| Re: Chip Selects for Plus 4 an C16?
Wrong.
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Posted By
Csabo
on 2021-05-20
15:01:31
| Re: Chip Selects for Plus 4 an C16?
Hey Superglob,
Sorry about the confusion around your question, obviously we're not all clear on what you're trying to do. This info should be more readily available on our site :-/ Anyway, let me try to clear some of this up.
This may be unrelated to your question, but...
- after writing to $FF3E, the memory will be mapped to $0000-$7FFF: RAM, $8000-$FCFF: ROM.
- after writing to $FF3F, the memory will be mapped to $0000-$FCFF: RAM
The chips can only be mapped to $8000-$BFFF / $C000-$FCFF (so, you cannot map ROM below $8000, no matter what). You can only control this from software, by writing to $FDDX. (On C64, apparently there are chip select signals on the expansion port, which control the memory layout, but there's no such thing on the C16/Plus4.)
Hope this helps! 
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Posted By
Superglob
on 2021-05-20
17:30:55
| Re: Chip Selects for Plus 4 an C16?
Thanks for clearing that up Csabo! Much appreciated
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