Hi Ruud, On 2013-06-16 22:18, Ruud@Baltissen.org wrote: > > The 14 pins one gives me head aches: > > > +------+ > +----- 2 -+ | +------+ > PHI2 -----+ | ?? +- 1 ---- 5 -+ | > +----- 3 -+ | | ?? +- 4 --- 9 of 175 > +------+ +-- 6 -+ | > | +------+ > IO1 -----------------------------+ > > Pins 8..13 are not used. > > > There aren't many ICs with outputs at pin 1 and 4. What immediately > came to my mind was the 7402. But pin 9 of the 175 has a rising > edge. OTOH, at the falling edge of IO1 the address should be valid > as well and that could work. But again the same problem: my IC > tester says it's not. We'll see tomorrow. > > But it could be that one of you know of ICs that I don't know and > still fit the description. > IMHO it fits fine with a 7402 - one of the few 74'ers with alternative pinouts and outputs on pin 1 and 4. What is I that makes you doubt that is it a 7402 quad 2-input NOR IC ? * pins 2, 3 basically inverts PHI2 - at rising edge of PHI2 output on pin 1 becomes low/0 * IO1 is active low/0 These two signals above fed to pins 5, 6 would give the rising edge on pin 4 - any other combination would result in low/0 - or am I missing some point here ? /Uffe Message was sent through the cbm-hackers mailing listReceived on 2013-06-17 20:00:04
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