piclist 2000\05\28\202332a >
Thread: Microcontroller with 4 USARTs and 40 pins
face picon face BY : Byron A Jeff email (remove spam text)

On Sun, May 28, 2000 at 06:21:24PM -0300, Edson Brusque wrote:
> > >If it don't say anything more, it may be the classic 8051's: one machine
> > >cycle is formed by twuelve clock cycles, and the instruction cycle
> > >depends on the particular instruction.
> > >If You want more speed enhacement look at Dallas MCS-51 compatible,
> hi-speed
> > >micros.
> > Or the AVR, at one xtal clock per instruction (a few take two). 8 mhz, but
> > that's 96 to an 8051 apparently.
>     Ok, but beside the Scenix, there's no 8-bit microcontroller capable of
> doing more than 20 MIPS???
>     And what about the 16-bit micros? Can it be a good option for my
> project? A US$10-20 microcontroller isn't very expensive to me if it can do
> all I need on this project.

A piece of advise. Stick to environments you know instead of striking out.
Especially when your striking out for more MIPS because you want them for
something that's easily done in hardware.

I'd advise sticking with PICs. Let me throw out a couple of suggestions.

1) I'm planning on using a Cirrus Logic CL-CD180 octart. Unfortunately Cirrus
Logic has obsoleted the part. In fact they've spun off their communcations line
into Basis Communications. I have a couple of samples and an incomplete
data sheet. If anyone has the pinout I'd really appreciate it. I liked the
part because of the number of serial ports and the fact that it came in a
84 pin PLCC package making it easy to use to hobby work. Basis Comm does have
an updated version the CL-CD1865. But it comes in a 100 pin PQFP. Not real
easy to prototype with.

2) My second choice was to build an intelligent UART out of a PIC. Specifically
for MIDI conversion of the stream into events with timestamps would be
very useful. Also having buffering so that the main processor can dump
events ahead of time and have the intelligent MIDI UART deliver them to the
channel at the appropriate time. Also doing MIDI channel mapping, splits and
volume control in the UART seems interesting. It's also interesting to consider
direct transmission of events from one UART to another bypassing the main

A single software channel can easily be handled by a 12C509 with a software
UART. Of course developing the UART code, the interface to the main processor,
(probably something I2Clike) would take some effort. But once it's done
any number of channels could be added to the system and the main system
wouldn't have to be uberpowered.

Maxim has an interesting discussion in their MAX3100 intro describing the
issues of software UARTs. You can find it here.


The bottom line IMHO is that the traditional approach is better than the
Winmodem approach because you end up having a highly overpowered processor
just so that you can have the MIPS to bit bang UARTS. Just remember that
8 12C509's will give you 8 MIPS just for the UARTS. Think about the
distributed processing solution.



In reply to: <01f501bfc8ea$afce5260$daa3f7c8@bigbru>; from brusque@FLYNET.COM.BR on Sun, May 28, 2000 at 06:21:24PM -0300
See also: www.piclist.com/techref/io/serials.htm?key=usart
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Subject (change) Microcontroller with 4 USARTs and 40 pins

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