On Wed, 19 Dec 2001, Baltissen, R (Ruud) wrote:
> Hallo William,
>
> > A logic probe would be safer. You would not be able to measure the
> > voltage, but you should be able to tell which is the program pin.
>
> What good is to know which pin is the program pin if you don't know where to
> apply the 25 V to?
>
> We have 24 pins:
> 1- 13 addresslines
> 2- 8 datalines
> 3- Vss = GND
> 4- Vcc
> 5- ChipSelect
>
> We can scratch 1 to 3 as possible candidates for the 25 V.
> Choosing pin 24 = Vcc for the 25 V means the 68764 needs an internal 5V
> regulator for supplying power to the rest of the IC not able to cope with
> the 25 V. Think of the heat generated using this construction.
> I favour the CS-pin, both as Vpp and program pin: apply 25 V the moment the
> address and data is valid. This also would mean that, when using an ordinary
> voltmeter, we would not measure 25 V but maybe something like 10 V. Using a
> scope would be better in this case.
I have checked the Promenade instruction manual. The program control word
is $30 which means:
25V
on pin 22
no program pulse required
no action on pin 22 on read
set standby level on pin 20 low
> > A logic probe would be safer.
>
> Yes, for the EPROM and the prommer. But can the probe handle 25 V? :)
It can if it has a fuse.
Message was sent through the cbm-hackers mailing list
Archive generated by hypermail 2.1.1.