Yes, but then again, the rom image is archived and distributed and
downloadable, and it's very easy to just re-program the chip if it ever
did get corrupted. The harm would just be spinning your wheels looking
for some other kind of hardware fault that day if it ever happens. So
it's not really that bad. It's not like it harms the machine or corrupts
something irreplaceable.
So, I think it's fine to pop a rom into your own machine.
But when designing any kind of project that other people will use as a
reference, or for selling a product to customers, I think in that case
the difference between not-likely and not-possible matters, and the I's
should be dotted and the T's should be crossed.
--
bkw
On 3/10/22 23:01, Stephen Adolph wrote:
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
