RE: General Instruments Capacitive Keyboard Encoder
> -Original Message- > From: Tony Duell [mailto:ard.p850...@gmail.com] > > On Wed, May 5, 2021 at 8:12 AM Paul Birkel wrote: > > > > > -Original Message- > > > From: Tony Duell [mailto:ard.p850...@gmail.com] > > > > > > > On Tue, May 4, 2021 at 10:33 AM Paul Birkel via cctalk > > > > wrote: > > > > > > > > The GI encoder is a DIP-40 labeled as "321239007 M2406-054-02 GI 8233 > > > > CBU > > > > TAIWAN". I seek technical documentation for this IC. > > > > > > You might take a look at the manuals here : > > > > > > http://cpu-ns32k.net/Whitechapel.html > > > > > > I am pretty sure there's a keyboard techincal description in 'binder > > > 1' and a reverse-engineered schematic in 'binder 2'. While it's not > > > quite the same IC, it's related and the power pins are in the right > > > place :-) > > > > > > Alas there is no real description of what that IC does or how to talk > > > to it from the 8039. It is designed to sit on the 8039 bus, it takes > > > in the multiplexed address/data bus, ALE, rd/ and wr/ > > > > The straight-thru wiring on ~RD and ~WR alongside ALE with no address > > decoding is IMO > > rather odd. I wonder how that design actually works (either assumes that > > it is the only writable > > device present, or actually latches 8 bits of address and shadows some > > valid ROM address) > > and then what gets written to the encoder for what purpos(es). > > Remember that the 8039 has separate program and data memory spaces. "Sokath, his eyes uncovered." Thank you Tony. Your notation observations both sound very reasonable to me. paul
Re: General Instruments Capacitive Keyboard Encoder
On Wed, May 5, 2021 at 8:12 AM Paul Birkel wrote: > > > -Original Message- > > From: Tony Duell [mailto:ard.p850...@gmail.com] > > > > > On Tue, May 4, 2021 at 10:33 AM Paul Birkel via cctalk > > > wrote: > > > > > > I'm currently reverse-engineering an AMPEX keyboard that uses capacitive > > > key > > > switches. The basic design employs a GI encoder coupled to an 8039 MCU > > > supplemented by a 2K EPROM and 74LS373 (used to latch the ROM address set > > > from Port A while Port A is then used to read data back from the ROM). > > > The > > > 8039 MCU drives a bit-banged serial interface. ... > > > > > > The GI encoder is a DIP-40 labeled as "321239007 M2406-054-02 GI 8233 > > > CBU > > > TAIWAN". I seek technical documentation for this IC. > > > > You might take a look at the manuals here : > > > > http://cpu-ns32k.net/Whitechapel.html > > > > I am pretty sure there's a keyboard techincal description in 'binder > > 1' and a reverse-engineered schematic in 'binder 2'. While it's not > > quite the same IC, it's related and the power pins are in the right > > place :-) > > > > Alas there is no real description of what that IC does or how to talk > > to it from the 8039. It is designed to sit on the 8039 bus, it takes > > in the multiplexed address/data bus, ALE, rd/ and wr/ > > Bingo. That's basically my circuit here (pin for pin) with minor differences > in RC values and a much more interesting serial interface (and a _four_ > finger salute no less! N-S-T-V Take that DOS ...), although mine supports a > buzzer/speaker. > > The principal inconsistency is that pin 25 is marked "CS" and left open in > the "binder 1" schematic (page 132 of 134), and then doesn't appear in your > hand-drawn schematic (page 7 of 24). In my circuit it's wired to the 8039 > ~PSEN. > > The straight-thru wiring on ~RD and ~WR alongside ALE with no address > decoding is IMO rather odd. I wonder how that design actually works (either > assumes that it is the only writable device present, or actually latches 8 > bits of address and shadows some valid ROM address) and then what gets > written to the encoder for what purpos(es). Disassembly of the EPROM should > answer those questions. My objective here is to replace the bit-banged > interface with a parallel interface emulating one for an Intel MDS-230. Remember that the 8039 has separate program and data memory spaces. PSEN/ (Program Store ENable) is asserted to access the ROM .If pin 25 of the keyboard scanner chip is CS, that might be Chip Select (active high), to ensure the chip is disabled on ROM accesses. Rd/ and Wr/ are asserted to access data memory. Here the only device is the keyboard scanner chip, so there's no need for address decoding. Since the keyboard scanner chip takes in ALE, there's a chance it uses the lower 8 address lines (multiplexed with the data bus) to select different internal registers, > > Two questions on notation.: > > 1. In the "binder 1" schematic pin 6 is marked as Ry and is pulled up > via resistor to +5v. On your hand-drawn schematic the corresponding pin > appears to be labeled "PVR". What might be the function of this pin? > > 2. In the "binder 1" schematic pin 15 is marked as Cm and is attached to > an RC circuit. On your hand-drawn schematic the corresponding pin appears to > be labeled "RC". C = 100 nF. What might be the function of this pin? I'm > guessing ~(Power On Reset) rather than as the basis for an on-chip oscillator > as seen in the AY-3-4592 pin 36 "RC" given the relatively high capacitance > value. My guess is that I called the first 'PUR' for pull-up resistor :-) It may actually set the sensitivity of the row inputs or somethng. The second may be an RC delay to allow the keyboard to settle. There's something similar in the PERQ2 keyboard which uses separate row and column chips. -tony
RE: General Instruments Capacitive Keyboard Encoder
> -Original Message- > From: Tony Duell [mailto:ard.p850...@gmail.com] > > > On Tue, May 4, 2021 at 10:33 AM Paul Birkel via cctalk > > wrote: > > > > I'm currently reverse-engineering an AMPEX keyboard that uses capacitive key > > switches. The basic design employs a GI encoder coupled to an 8039 MCU > > supplemented by a 2K EPROM and 74LS373 (used to latch the ROM address set > > from Port A while Port A is then used to read data back from the ROM). The > > 8039 MCU drives a bit-banged serial interface. ... > > > > The GI encoder is a DIP-40 labeled as "321239007 M2406-054-02 GI 8233 CBU > > TAIWAN". I seek technical documentation for this IC. > > You might take a look at the manuals here : > > http://cpu-ns32k.net/Whitechapel.html > > I am pretty sure there's a keyboard techincal description in 'binder > 1' and a reverse-engineered schematic in 'binder 2'. While it's not > quite the same IC, it's related and the power pins are in the right > place :-) > > Alas there is no real description of what that IC does or how to talk > to it from the 8039. It is designed to sit on the 8039 bus, it takes > in the multiplexed address/data bus, ALE, rd/ and wr/ Bingo. That's basically my circuit here (pin for pin) with minor differences in RC values and a much more interesting serial interface (and a _four_ finger salute no less! N-S-T-V Take that DOS ...), although mine supports a buzzer/speaker. The principal inconsistency is that pin 25 is marked "CS" and left open in the "binder 1" schematic (page 132 of 134), and then doesn't appear in your hand-drawn schematic (page 7 of 24). In my circuit it's wired to the 8039 ~PSEN. The straight-thru wiring on ~RD and ~WR alongside ALE with no address decoding is IMO rather odd. I wonder how that design actually works (either assumes that it is the only writable device present, or actually latches 8 bits of address and shadows some valid ROM address) and then what gets written to the encoder for what purpos(es). Disassembly of the EPROM should answer those questions. My objective here is to replace the bit-banged interface with a parallel interface emulating one for an Intel MDS-230. Two questions on notation.: 1. In the "binder 1" schematic pin 6 is marked as Ry and is pulled up via resistor to +5v. On your hand-drawn schematic the corresponding pin appears to be labeled "PVR". What might be the function of this pin? 2. In the "binder 1" schematic pin 15 is marked as Cm and is attached to an RC circuit. On your hand-drawn schematic the corresponding pin appears to be labeled "RC". C = 100 nF. What might be the function of this pin? I'm guessing ~(Power On Reset) rather than as the basis for an on-chip oscillator as seen in the AY-3-4592 pin 36 "RC" given the relatively high capacitance value. Thank you for these new breadcrumbs. paul
Re: General Instruments Capacitive Keyboard Encoder
On Tue, May 4, 2021 at 10:33 AM Paul Birkel via cctalk wrote: > > I'm currently reverse-engineering an AMPEX keyboard that uses capacitive key > switches. The basic design employs a GI encoder coupled to an 8039 MCU > supplemented by a 2K EPROM and 74LS373 (used to latch the ROM address set > from Port A while Port A is then used to read data back from the ROM). The > 8039 MCU drives a bit-banged serial interface. The PCB identifies itself as > AMPEX on the coper foil, although the key switch mounting-plate actually has > a "General Instruments Quality Accepted" sticker. The EPROM is labeled > "3512663-03 Copyright 1983 AMPEX CORP". > > > > The GI encoder is a DIP-40 labeled as "321239007 M2406-054-02 GI 8233 CBU > TAIWAN". I seek technical documentation for this IC. You might take a look at the manuals here : http://cpu-ns32k.net/Whitechapel.html I am pretty sure there's a keyboard techincal description in 'binder 1' and a reverse-engineered schematic in 'binder 2'. While it's not quite the same IC, it's related and the power pins are in the right place :-) Alas there is no real description of what that IC does or how to talk to it from the 8039. It is designed to sit on the 8039 bus, it takes in the multiplexed address/data bus, ALE, rd/ and wr/ -tony
RE: General Instruments Capacitive Keyboard Encoder
> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Al Kossow > via cctalk > Sent: Tuesday, May 04, 2021 9:48 AM > To: cctalk@classiccmp.org > Subject: Re: General Instruments Capacitive Keyboard Encoder > > On 5/4/21 2:33 AM, Paul Birkel via cctalk wrote: > > I'm currently reverse-engineering an AMPEX keyboard that uses capacitive key > > switches. > > did all of the square foil and foam pads disintegrate in it? It uses individual sprung metal leaves, with the exception of the caps-lock key which has a central LED and around that an annular square foil/pad that is in fine shape. It's all nicely constructed; the case even includes a spray-on metallized surface that is connected via a sprung contact to the cable shield and the switch-body retaining plate. -
Re: General Instruments Capacitive Keyboard Encoder
On 5/4/21 2:33 AM, Paul Birkel via cctalk wrote: I'm currently reverse-engineering an AMPEX keyboard that uses capacitive key switches. did all of the square foil and foam pads disintegrate in it?
General Instruments Capacitive Keyboard Encoder
I'm currently reverse-engineering an AMPEX keyboard that uses capacitive key switches. The basic design employs a GI encoder coupled to an 8039 MCU supplemented by a 2K EPROM and 74LS373 (used to latch the ROM address set from Port A while Port A is then used to read data back from the ROM). The 8039 MCU drives a bit-banged serial interface. The PCB identifies itself as AMPEX on the coper foil, although the key switch mounting-plate actually has a "General Instruments Quality Accepted" sticker. The EPROM is labeled "3512663-03 Copyright 1983 AMPEX CORP". The GI encoder is a DIP-40 labeled as "321239007 M2406-054-02 GI 8233 CBU TAIWAN". I seek technical documentation for this IC. It evidently is not a relabeled simple variant of the documented AY-3-4592 as it does not multiplex the input side of the matrix (sense lines), there are fewer output data lines, and the power pins are non-standard (Vcc = pin 37; GND = pin 16). Reverse engineering identifies this M2406-054-02 as supporting an 8 column by 16 row (3 unused in my case) matrix plus 8 output data lines. I can identify analogs of several pins on the AY-3-4592. My interpretation of the pin uses is that the necessary key-scanning behavior is generated using the 8039 ALE line (pin 11) as the encoder clock input. Proper documentation for this IC would be nice to come by! Pointers and suggestions appreciated. Thank you, paul
