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memory mapped device without CRU? enablement or with < 0x1000 crubase


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#1 jedimatt42 ONLINE  

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Posted Sat Feb 16, 2019 7:20 PM

Ok, so I understand the SID Master 99 is mapped into the 0x4000 - 0x5FFF space when no other DSR roms are mapped in. 

 

Does someone know by what mechanism that is done? 

 

Is it that it decodes cru bit 0 of all card spaces ( effectively every 128'th cru-bit ) and tracks if anything else is on?  Assuming only one will be on at a time? 

 

Then is the remaining address space shareable if additional device memory addresses are fully decoded? 

 

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Also, I've seen that cards could use crubase's below 0x1000 as long as they don't need to be found by a DSRLNK routine. Were any such devices ever produced?  If there is no ROM it is seems to me it requires community convention to allocate crubases do not collide, or memory addresses within a shared crubase that do not collide.

 

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I've got a YM2413 (OPLL) FM synthesizer chip I'd like to hook up to the 4A...  I'm just trying to decide how I want to make it addressable.   The minimum requirement is 2 memory mapped write-only bytes.

 

-M@



#2 Tursi OFFLINE  

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Posted Sat Feb 16, 2019 9:33 PM

As it was explained to me, it pages in when there is a CRU access less than >1000. The idea was that then it was always available in (for instance) Extended BASIC, because the keyboard scan would switch it in.

#3 helocast OFFLINE  

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Posted Sat Feb 16, 2019 10:09 PM

Ok, so I understand the SID Master 99 is mapped into the 0x4000 - 0x5FFF space when no other DSR roms are mapped in. 

 

Does someone know by what mechanism that is done? 

 

Is it that it decodes cru bit 0 of all card spaces ( effectively every 128'th cru-bit ) and tracks if anything else is on?  Assuming only one will be on at a time? 

 

Then is the remaining address space shareable if additional device memory addresses are fully decoded? 

 

I agree with Tursi as I don't see much on the card in the way of decode, but I did find a small snippet of what I'm assuming is the manual:

Attached Files



#4 jedimatt42 ONLINE  

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Posted Sat Feb 16, 2019 10:20 PM

Oh, $@#$@, that is (possibly) a bit more intrusive than I imagined...    So, I've just observed that running around in Easy-Bug where I commonly enable TIPI, the Sid Master 99 turns off for a moment, but then of course Easy-Bug prompts me again which (must) re-enables it...  So technically I have 2 devices in the same address space right now. (from a high-level point of view)   Luckily write-operations and read operations further divide address space electrically... or can, anyway...  

 

ok, so technically that answers the question about what crubases below >1000 are available... none...

 

-M@



#5 jedimatt42 ONLINE  

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Posted Sat Feb 16, 2019 10:27 PM

Ah, with Helocast's data, I am overlapped when I debug TIPI in mini-mem, as tipi's output registers are at 0x5FFD and 0x5FFF....  my SID probably goes nuts very quietly icon_smile.gif when I'm manually testing TIPI...

 

-M@



#6 apersson850 OFFLINE  

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Posted Mon Feb 18, 2019 2:11 AM

My own internal (in the console) RAM expansion uses CRU addresses at >400 to enable and disable banks of that memory. I can enable RAM in the DSR space (and everywhere else) with a CRU access based at >400.

 

This is just to prove that such assumptions as the SID Master 99 does are always dangerous. As is my own assumption, that CRU address >400 will not interfere with anything.



#7 Vorticon OFFLINE  

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Posted Mon Feb 18, 2019 7:11 AM

Great info on the SID card. I have one and have never used it... It's a damn shame if you ask me, particularly since it can be easily accessed from almost any language.

I wonder if an external version could be made so as not to require a PBox...



#8 TheBF ONLINE  

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Posted Mon Feb 18, 2019 8:03 AM

What does a SID 99card do?



#9 Lee Stewart OFFLINE  

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Posted Mon Feb 18, 2019 9:06 AM

What does a SID 99card do?

 

 

This from Marc Hull’s website:

 

What is SID Master 99?
Sid Master 99 is a PEB interface cards that integrates an MOS 6581 or MOS 8580 SID chip into the architecture of the TI99/4A as a memory mapped device.   It can be accessed through any  language that allows normal CPU memory access such as assembly language, Extended BASIC etc.  If you can do a CALL LOAD or equivalent then you can access the SID chip.   A new vista of never before heard sounds can now be played through your TI99/4A.  No sound cables required.  It is completely compatible with the existing sound chip on the computer and plays through your monitor or TV.

 

...lee






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