Question ref 84-86 Sunbirds

[Ludis Langens]

bruce plecan <nacelp at bright.net> wrote:
> What is a 1K*8 bipolar prom??..
> Is it a replaceable chip?.  ala resistor network?

It is like a small EPROM.  However, instead of using NMOS or CMOS
circuitry, it uses TTL - that's what bipolar means.  Further, instead of
trapping some electrons in an insulated pocket, it has metallic fuses
for the memory array.  To program a bit, you simply blow a fuse.  Hence,
they are not erasable.

Bipolar PROMs are low capacity, fast access, power hungry, and obsolete.

The PROM in question was of the N82S181 type.  It uses a 24 pin
package.  The pinout is the same as a 24 pin EPROM, except pin 21 =
~CS1, pin 20 = ~CS2, pin 19 = CS3, and pin 18 = CS4.  Jamaco sells them
for $4.25.  Their cheapest EPROM (with eight times the capacity) is
$2.75.

               unsigned long BinToBCD(unsigned long i) {unsigned long t;
Ludis Langens     return i ? (t = BinToBCD(i >> 1), (t << 1) + (i & 1) + 
ludis at cruzers.com            (t + 858993459 >> 2 & 572662306) * 3) : 0;}