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Reverse-Engineering the Speech Processor ROM [message #10681 is a reply to message #10678] Sun, 07 April 2024 11:24 Go to previous messageGo to previous message
jayindallas is currently offline  jayindallas
Messages: 110
Registered: June 2021
Senior Member
Speech Processor External ROM Substitute: Possible? PROBABLY... YES
My 'Speech Processor' (SP) study is still at the block & code level, but it seems reasonable that one could design an external interface around parallel-bus memory to replace a 'Speech Processor external ROM' (SPR).

It makes sense that anyone developing code and data for a SPR would need a construct like this to TEST their development before paying the expense of making masked-ROM SPRs. 'General Instruments' (GI) may have sold a development board to do this or documented a circuit interface.

Speech Processor External ROM Substitute: Logic Interfaced or Microcontroller?
While developing a working interface with the SP or between the SP and SPR... using a microcontroller would probably be more advantageous, because changes are only made in software; the time to "CODE...LOAD...RUN" is very quick compared to hardware circuit changes and waiting for components to arrive.

In general use of an option like this, it would depend upon each hobbyist's comfort using a microcontroller in this way. The popularity of the Arduino has increased the familiarity with microcontroller use. Making use of this advantageous microcontroller option might to useful goal for many hobbyist to add to their abilities... or as I always phrased it, "adding something new to my bag-of-tricks" :)

Its necessary to assure that the microcontroller you prefer to use, is fast enough (with code execution time) to control TTL signal emulation by programming. AJ Lynch provided a good timing example in his previous message. Finding a +5Vdc microcontroller would also simplify things when interfacing vintage components.

[Updated on: Mon, 08 April 2024 06:47]

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