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 >> >
