Hi All, I’m not sure leaving a CMOS chip input open is a good idea. The OE and PGM/ should be pulled to their respective enabled states or the output may not be predictable. I suspect Vpp is not necessary to connect.
Atsushi On Jul 4, 2017, at 8:01 PM, Gary Weber <m100l...@gweber.org> wrote: > I found some useful information from assuearcade.com. It seems there are > some EPROM parts that would work as a replacement for the NEC PC-8300 system > masked ROM. > > - - - - - - - > > Compatible EPROMS: NEC 27C1000 & HN27C301G. Those are the ONLY chips you can > use. They are 32 pin 1M EPROMs but are pin compatible with 28 pin 1M > uPD231000 mask ROM. All you need to do is join a wire from pin 30 to pin 32 > for VCC. The top 4 pins will just hang out of the socket, don't worry about > them. > > MASKED ROM EPROM > (1M) 128k x 8 mask rom (TC531000) (1M) 128k x 8 EPROM (HN27C301) > (23C1000) (NEC 27C1000) > Vpp +-v-+ 32 Vcc \ > OE 2 | | 31 PGM/ | <-- Wire > pin 32 to 30 for Vcc to be on pin 28 of socket > A15 1 +-v-+ 28 VCC A15 3 | | 30 nc / > A12 2 | | 27 A14 A12 4 | | 29 A14 > A7 3 | | 26 A13 A7 5 | | 28 A13 > A6 4 | | 25 A8 A6 6 | | 27 A8 > A5 5 | | 24 A9 A5 7 | | 26 A9 > A4 6 | | 23 A11 A4 8 | | 25 A11 > A3 7 | | 22 A16 A3 9 | | 24 A16 > A2 8 | | 21 A10 A2 10 | | 23 A10 > A1 9 | | 20 CE/ A1 11 | | 22 CE/ > A0 10 | | 19 D7 A0 12 | | 21 D7 > D0 11 | | 18 D6 D0 13 | | 20 D6 > D1 12 | | 17 D5 D1 14 | | 19 D5 > D2 13 | | 16 D4 D2 15 | | 18 D4 > GND 14 +---+ 15 D3 GND 16 +---+ 17 D3 > > I suppose using an adapter board would look cleaner, but honestly having a > few pins hanging off the socket may not be that big of a deal.. > > Anyway, sorry for all the spam from me today. I got a bit excited! ;-) > > Gary > > > On Tue, Jul 4, 2017 at 4:01 PM, Gary Weber <m100l...@gweber.org> wrote: > I keep trying to attach photos to this post thinking I can make them small > enough. I *swear* I keep saving them as a 57k JPG but when I upload it, > they're 200k and get rejected. Okay, let's try this a different way! Just > embedded links this time... > > Okay, here's what I found in the NEC PC-8300 Technical Reference, and right > there in plain sight, all is revealed: > http://i133.photobucket.com/albums/q53/gweber68/NEC_PC-8300_ROM_Bank_Select_zpsfnltzdo7.jpg > > The 128k mask PROM is the NEC uPD23C1000A. And here's the datasheet on the > part itself: > http://www.datasheet4u.com/datasheet-pdf/NECElectronics/UPD23C1000A/pdf.php?id=539613 > > Seems putting a new NEC PC-8300 ROM together might be within reach, for those > so inclined. :) > > Gary > > On Sun, Feb 19, 2017 at 1:12 PM, Stephen Adolph <twospru...@gmail.com> wrote: > yah, thx. I think it needs to be buzzed out a bit to confirm the > actual pinout... > > On Sun, Feb 19, 2017 at 12:20 PM, Kurt McCullum <kurt.mccul...@att.net> wrote: > > Steve, > > > > Keep in mind that I am guessing on the PROM based on the limited number of > > 128k 28 pin PROMs available at that time. That's a pinout for the NEC PROM > > but I don't know if that is the actual part which was used. There should be > > a number on the chip that may lead to the answer. > > > > Kurt > > > > -----Original Message----- > > From: M100 [mailto:m100-boun...@lists.bitchin100.com] On Behalf Of Stephen > > Adolph > > Sent: Sunday, February 19, 2017 5:13 AM > > To: Model 100 Discussion <m100@lists.bitchin100.com> > > Subject: Re: [M100] Parts for an NEC PC-8300 > > > > .. comparing a 27C1001 pinout to the one from Kurt, it looks like it may > > just be possible to stuff a 27C1001 and wire up only a couple of signals. > > > > > > On Sat, Feb 18, 2017 at 8:12 PM, Stephen Adolph <twospru...@gmail.com> > > wrote: > >> come to think of it, you could probably tie /CE and /OE together. > >> > >> On Sat, Feb 18, 2017 at 8:08 PM, Stephen Adolph <twospru...@gmail.com> > >> wrote: > >>> I did not grasp how much information is in that 500MB tech reference > >>> doc for the 8300. Wow! > >>> > >>> probably the best documented Model T. > >>> > >>> It is clear that the ROM is 128KB, and I think it is also clear that > >>> without some custom solution, one can't make a replacement main rom > >>> for the 8300 easily. At best you might be able to program a 27C1001, > >>> and then do a custom adapter board. > >>> > >>> A normal eeprom needs both a chip select and an output enable, so > >>> some extra logic might be needed too. > > > >
