I think that means the old 27C256 in the T102 is a bad idea, without an adapter board or a wire to +5V.
On Thu, Mar 10, 2022 at 9:52 PM Brian White <[email protected]> wrote: > I always tie it to vcc, with a pullup so that a programmer can still > override it. > > As you saw yourself, every datasheet always says to pin to vcc or lower, > usually preferring vcc. > > I think the harm is just the risk of reaching vpp randomly if left > flapping, so you might corrupt the data. Probably *almost* never happens, > but the datasheet directions implies that there is no equivalent of a > built-in pullup, which means the pin is free to spike even from say, static. > > Seperately, I would always nail down *any* input just on principle, and > especially any control input. > > -- > bkw > > On Thu, Mar 10, 2022, 3:32 PM Mike Stein <[email protected]> wrote: > >> Don't know about the 27C256 but experience with 2732s was that with some >> manufacturers you could get away with leaving it to float whereas on others >> you had to explicitly pull it high (which would be my recommendation). >> >> m >> >> On Thu, Mar 10, 2022 at 2:20 PM Stephen Adolph <[email protected]> >> wrote: >> >>> Quick one for the crowd. >>> On a 27C256, I have always thought you could ignore Vpp for normal use, >>> and only use it for programming. >>> >>> So, you could plug a 27C256 where the main rom lives in a T102 or T200, >>> or UK M100, or KC-85, or M10. whew. >>> >>> However, when I look at datasheets for 27C256, they all say normal >>> condition on pin 1 is VCC!!! >>> >>> What gives? >>> Is it ok to float pin 1, or really should we be connecting pin 1 to plus >>> 5V? >>> >>> thanks >>> Steve >>> >>
