atari avg asic (again)

Ok, I'm still looking at this...

The good news:

A 44 pin TQFP does indeed sit inside the footprint of a 40 pin DIP (.6") part.

The Lattice ISPLSI1016 is available in the 44 pin TQFP.

The Lattice 1016 has 96 registers which are great for that 4 word deep stack.

The bad news:

The TQFP is $1 more per part. (no biggie)

The TQFP has about 28 days lead time. (ehhhh...)

The trace width for a TQFP is smaller than the AP Circuits-type (aka,
affordable) boardhouses can produce. (damn)

The 1016 has 4 inputs and 32 I/O's = 36. The Atari AVG uses 38. (Ahhh, hell.)

Lattice is doing something sneaky marketing-wise in that it looks like
there are multiple registers per macrocell, so macrocells get eaten with
register bits (but not as fast as say a 22V10 type architecture like the
2032 or something).

----
I think I can get around the number of inputs...  The best way might be
just to take something like a 16R8 (22V10 would be easier) that implements
all the misc logic and stack pointer.  I can move 7 inputs to that, and
have five outputs that go to the CPLD.  That saves 2 pins on the CPLD,
which should make it fit.  BARELY.
That still doesn't solve the board fabrication issues. :-(
I'm thinking 1016 + 22V10 (or a little less) + a pcb about twice the size
of a regular 40 pin dip...
-Clay
Clayton N. Cowgill                                  Engineering Manager
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