Andy, again the problem is implementing the FIFO. The ISA interface and
FIFO control is trivial. Since you already have the design in 2 FIFO's and a
22V10, moving the FIFO to a CPLD would dramatically raise the cost and it
would require a large device due to the number of internal registers needed.
Lattice and others have devices with internal FIFO's but they are very
expensive and large, typically over 200 pins in xQFP packages. When
designing custom chips there is always a `battle' between internal resources
and available I/O. In the above case, you would be using a large portion of
the internal resources and a small fraction of the I/O but you will be
paying for it...

   Without knowing the details of the design, I would take a hard look at
how large a FIFO you really need. For example 16 Bytes could easily fit in a
smaller CPLD.

   I'll admit I haven't thought this through but I was thinking of using
external logic to control a dual-port SRAM. In this case, you are just
implementing a dual FIFO with the advantage of using one chip for data
storage. There is a suitable Lattice CPLD that comes in a 68-pin PLCC or
100-pin TQFP (14mm x 14mm) package. This would cut board `real-estate' by
more than half but it might increase the cost...

   Believe me, I could use the work right now but unless board space is
`mission critical' compared to cost, I think the existing design is more
cost-effective depending on how much you are paying for the 7201s.

   - Tom

At 10:43 AM 8/20/99 -0400, Andy Kunz wrote:
>Board space is the problem.  We have two IDT 7201 FIFOs and a GAL22V10 on
>it now, and it would sure be nice to get the whole mess into one small
>package.  Also simplify the snot out of routing it.
>
>I don't care whose parts get used, so long as it works.  Lattice is a good
>choice by me, since they have good local support from the vendor here.
>
>What would it take to convince you to write the logic (I have the 22V20
>source I can send you).
>
>Andy


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)