🚀 go-pugleaf

The original PALs (by MMI?) were bipolar devices, the ever-popular
16R8 and 16L8 being typical devices.  These had a raw speed of perhaps
15ns tpd in-to-unregistered-out (typical speeds given), and consumed
about 140 mA @ 5V.  These were quickly followed by "half-power" devices
(25 ns, 75 mA).  Both of these families remain very popular, with the low-
power parts being most popular; the speeds being in the LSTTL ballpark.

The advantage of these PALS over random logic is board area, flexability,
and a "flattening" effect on the logic, yielding faster performance than
the typical TTL equivalent.  The disadvantages are generally higher cost
and increased power consumption.  The 16L8 has 10 inputs, one output, and
7 selectable inputs-or-outputs.  There are higher density bipolar PALS as well.

CMOS PALs were first introduced by Harris (I think) and were "zero standby
power" types, but were significantly slower than the bipolar PALS.  Altera
(second-sourced by Intel) introduced the EP300 PAL which was moderate power,
good speed, and had a very flexable "output macrocell" structure.  Altera, and
other manufacturers have followed up with larger, faster, lower-power devices.

Ballpark data:

Part No.    Vendor	Tpd max	    ICC (max idle)    Price (moderate qty)
16L8	    everyone	25ns	    180mA	    $1.00 ?
16L8 lowpwr everyone	35ns	     90mA	    $1.00 ?
16CL8 cmos  TI		55ns	    100uA	    ?
EP310 cmos  Altera	35ns	     30mA	    $5.00 ?
EP320 cmos  Altera	25ns	    150uA	    $7.00 ?

These are all 20-pin PALS.  The Altera parts are available with a windowed lid
so they can be erased with an EPROM eraser if you goof (or if marketing
changes their minds).  The bipolar PALS are one-shot devices.  Unlike EPROM
vendors, the cmos PAL suppliers are _very_ reluctant to release the programming
specs, so it is difficult to roll your own programmer.  I've not even touched
on the many more specialized state-machine type PALS or the larger devices.
All prices are guestimates, your mileage may vary.  Other vendors include
National Semiconductor, AMD, and many others.


-- 
Paul M. Elliott      Optilink Corporation     (707) 795-9444
           {pyramid,pixar,tekbspa}!optilink!elliott
                  "The dog ate my disclaimer."