27 Jan
1999
27 Jan
'99
11:25 a.m.
HI Dwight and all,
At 03:54 PM 1/27/99 -0800, Dwight wrote:
Programming the 1702A's
Well in some sence I have a little egg on my face.
The programmer I have was infact designed for
1702A's but doesn't do it following
the specifications.
First 1702 versus 1702A's. As was mentioned, the
1702's couldn't take the same duty cycle by 10X.
It isn't true that you can take a 1702 programmer
and program 1702A but you can take a 1702A programmer
and slow down the pulse rate and program 1702's.
The difference is that the 1702A's require an address
complement phase at the start of the cycle. This phase
doesn't effect the 1702's so the only issue is repeat
rate.
Now to the issue with my MP7-03 board. The first PROM
I tried was either originally blown or I blew it out.
The programming voltage was about 53 volts. I cranked
it down to 47 volts and tried another PROM and it now
works fine.
Cool that you can program them.
I looked at my manual and it was for the MP7-03 too. In my schematic, there
are 7486 gates in the 8 address lines to invert the data. They are inverted
for 60 microseconds by a monostable. The signal goes from (edge connector)
pin #7 to the 7486's connected to pin #39. Does anyonne know for what the
inversion of
the addresses is required?
Have not traced all the timing as you have to see the resultant setup
times, etc. Of course the MP7-03 uses positive voltages, as the voltage
reference point is different than the data sheets. Am nor sure if I figured
out the logic levels. You program a "1" with a negative voltage (data
sheet) = positive in the MP7-03. I guess if the programmed data or
addresses come out complemented, you got those levels inverted, and you do
it again.
It looks also that you can program 1 byte at a time (32 cycles). In the
later 2708, the data sheets says you have to cycle through all locations.
Does anyone know if this is for the thermal duty cycles of the address
lines? This restriction was removed for the later 2716.
-Dave