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Title: E-Chip masked ROM? Post by: Escobar on June 04, 2020, 10:45:34 AM Hi everyone!
A question about the Emax 1 E-chip: Does the E-chip contains any kind of memory, like masked ROM or such? Or is it completely controlled by the IP349 eprom? It would be interesting to get that clarified. Thanks for answers in advance. Title: Re: E-Chip masked ROM? Post by: Freddy on June 05, 2020, 05:50:16 AM Checked the service manual. From my understanding - no.
Title: Re: E-Chip masked ROM? Post by: Escobar on June 05, 2020, 10:05:35 AM Thank you Freddy for your answer, I do have the service manual also but I wasn't sure if I have missed something.
The reason for my question is that while I was checking out the schematics - specially the schematics over the E-chip and sound memory - I noticed a very interesting thing; the address lines for sound memory (SMA 0 - SMA 19) the E-chip only make use of the first 19 address lines. Line #20 (SMA19) has no connection at all and are left unused. My theory is that this unused address line could be used for expanding the sound memory with additional 512k dram. The line could be used as a select signal in four 1:2 demultiplexers similar to SMA lines #8, #11, and #12. You would only need to demultiplex the four control lines: SDOE (WE), CAS, RAS0, and RAS1 coming out from the PAL chip (IC49) to make it work. Ofcourse one would probably need to update the firmware also. Just an idea.. Thanks again for your answer. |