27 Jun
2005
27 Jun
'05
5:59 p.m.
the Intel data book makes it very clear you do have to
program
all locations.
The unchanged ones have to be reprogrammed with their
existing
contents, you can't skip over them.
Not true on both counts, you only need to go through the program
cycle for bytes that need to be programmed and if you want to leave
a byte unchanged but still go through the program cycle then you
set the data to $FF as bits can't be programmed high.
What the data sheets say often did differ from the practice, even
on official programmers.
I used to use 2708s in CB to 11m conversions and got away without
the -5v supply by using a lamp to illuminate the chip and generate
the -ve bias photoelectrically, this only worked with one brand of
EPROM though.
Lee.
.
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28 Jun
28 Jun
10:34 a.m.
the Intel data book makes it very clear you do
have to program
all locations.
The unchanged ones have to be reprogrammed with
their existing
contents, you can't skip over them.
Not true on both counts, you only need to go through the program
cycle for bytes that need to be programmed and if you want to leave
a byte unchanged but still go through the program cycle then you
set the data to $FF as bits can't be programmed high.
What the data sheets say often did differ from the practice, even
on official programmers.
Maybe so. It probably works fine. But I will not deliberately go against
the manufacturer's specifications. It may save a couple of minutes now,
but it may also waste a few hours later tracking down an obscure bug....
I used to use 2708s in CB to 11m conversions and got away without
the -5v supply by using a lamp to illuminate the chip and generate
the -ve bias photoelectrically, this only worked with one brand of
EPROM though.
I'd much rather use a charge pump circuit and do it right.
-tony
7117
days inactive
7117
days old
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