Thanks.

I looked at this part early on, but it has no FIFO so the DSP would be
interrupted for every 8 bit transmit.  Currently a DMA buffer is used on the
serial port so the DSP is not interrupted at all.  Haven't looked at the new
PIC DSP enough to notice if there are DMA's - almost mandatory.  Maybe I
should look at it ....

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Matt Pobursky
Sent: Monday, August 20, 2001 1:15 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: SPI to Serial


You also might look at Maxim's MAX3100 series SPI based UART chip. It sounds
ideal for your application. It has an external interrupt pin as well. I'm
not
sure about non-standard baud rates, but I'm guessing that since it has an
external clock input you should be able to find a clock (crystal) frequency
that will work for you.

http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=1731

Matt Pobursky
Maximum Performance Systems

On Mon, 20 Aug 2001 10:39:20 -0500, Ed Browne, Precision Electronic
Solutions
wrote:
>Hi, all.
>
>I am building an interface between an ADSP2181 SPORT (serial port) and an
>RS232.  I have been able to make the DSP talk SPI before, so I thought a
>fast PIC may be able to do the conversion.  Selected PIC for this project
is
>an 'F877.  I had hoped to spurt SPI data out as a very fast stream,
>concurrently building the packet frame, then resend it as a more or less
>continuous asynchronous stream.  The problem gets further complicated
>because the RS232 is at 220.5kbaud - fast and non standard.  That problem
is
>solved by judicious selection of the crystal - either 14.318MHz or 18MHz.
>
>The DSP is a battery powered data acquisition system interrupt driven by an
>ADC.  Data is continuous and not all the SPORT handshake lines are
>available.  The DSP does some pretty serious filtering before passing the
>data so tasks are already pretty tight and optimized: get data, filter,
send
>data.  It already works and works well - 1 bit in 20 noise after a gain of
>103 (like I said, lots of filtering):-).
>
>My problem is this:  Using PICC, I have written simple minded code to
>generate data so I can see if the PIC can keep up.  RS232 seems to be able
>to, but [[[I have seen very long latencies between SPI words (operating at
>CLK/4)]]].  Is this normal?  If these can be shortened, how and how much?
I
>have browsed archives and am starting the process of understanding the
>compiler listing to see if there is something obvious.
>

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