On Thursday, Apr 8, 2004, at 08:01 US/Pacific, Andrew Kilpatrick wrote:

> I was wondering about maybe doing it just with the computer. I
> read the datasheet for the National 16550, and it seems that with
> some DMA action, it would be pretty efficient to send with the PC
> directly.

Is it really possible to use DMA with the async chip(set) in modern
PCs?  I don't recall that being possible originally (8250 uart, 8237
DMA), but
things are more integrated these days.  OTOH, it certainly has LOOKED
like the major 'advance' in UARTS has been deeper FIFOs, strongly
implying no DMA capability.  DMA of async data is quite a can of
worms...

You could look at old-style hardware uarts.  I made a newswire speed
conversion circuit with a couple of back-to-back 6402 uarts with
perhaps a one-shot and some BRG circuitry.  I don't recall whether the
6402 goes fast enough for your application, but it was a pretty trivial
circuit, and 6402s are still available from surplus dealers ($2.45 at
bgmicro.)

BillW

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