[TI-H] Re: building a TI92plus module

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[TI-H] Re: building a TI92plus module

docydoc wrote:

>No, not strictly necessary but some evil programs might overwrite your FLASH and
>that
>is not so nice. Even if a program does not intentionally at least an external
>switch should
>be used to protect some areas (e.g. the certificate's area and boot-strap if it's
>inside there)
>  
>
Its not very likely that a program unintentinally overwrites flash. I 
havn't seen any flash chips yet that allow normal writes as to
a memory chip.
You have to issue special commands to it, to write enable blocks, and to 
write the actual data (with a necessary erase first since you can only 
change bits one way, not the other with writes, without erase)

A switch isn't much work though, and probably a good idea anyway.

>btw: Has anyone ever experienced the situation of doint an update and it fails in
>the middle?
>Does the TI get dead (nodisplay, nothing or is it still "flashable"), like some
>cell phones.
>(e.g. N*kia's have there boot strap in the DSP itself so they r always updateable
>but Slemens
>is really delicate and sometimes extremly bitchy :-) but that's off topic, so I
>stop.
>  
>
There is a boot loader in the first ever writeprotected 64KBs that kick 
in if the actual AMS fails.

>>There are some informations that I need but I couldn't find: how the
>>ti-92 addresses the external rom and ram: addresses and wo4rd length (it seems
>>16 bit words, al long as there isn't a0 and there are 16 data pins, but
>>on one of ther previous links there's a 8 bit memory chip connected.
>>I'm asking the authors...
>>    
>>
>
>As far as I remember ther's a MC68ooo inside (or emulated?) This processor does
>not necessarily need a0. The 68k has a LSB and USB (lower and upper significant
>byte)
>Pin to indicate which half of the 16bit wide word at it's data bus is needed if in
>byte mode.
>  
>
And if you think about it, a LSB/USB pin work exactly as an a0 pin.
I guess the difference is more internal, and in the name of the pin then 
in how it actually works for a HW builder.

I unfortunatly know nothing about the plus module so I can't help much.
If you just figure out the pinout it probably isn't that hard to build.

Does the plus module also come with a processor inside?
That might open interesting possibilities to change it to something more 
powerful... :)
maybe a 68020 or 040 or something would be easiest :) ( I think at least 
one of them are instruction compatible with the 68000)
Would probably create timeing problems though, and possibly need rom 
patches.

-- Olle
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