Re: Cascade MCU

From: Ulf Samuelsson (ulf_at_atmel.nospam.com)
Date: 11/13/04 

Date: Sat, 13 Nov 2004 21:17:36 +0100

"terry" <leonlai2k@yahoo.com> skrev i meddelandet
news:9904d48.0411130605.495afc36@posting.google.com...
> Jim Granville <no.spam@designtools.co.nz> wrote in message
news:<Vbild.1109$3U4.98865@news02.tsnz.net>...
> > terry wrote:
> > > Hi,
> > >
> > > I have an idea but not known whether it is possible.
> > >
> > > During prototype development major MCUs with DIP package only have 40
> > > maximum number of pins. However, sometimes we need to use more I/Os
> > > when many external devices exist. And MCU with more than 40 pins
> > > always do not have DIP package so that PCB must be manufacured before
> > > further development.
> > >
> > > So I have a silly question whether 2 or more MCU could be easily
> > > cascaded?
> >
> > Yes.
> > If you want to simply expand the IO, there are i2c and SPI
> > peripheral IO expansion devices.
> >
> > If you want many 'like' devices, then ones with SPI hardware
> > will cascade easily, in a simple daisy chain, and ones with
> > UARTS can also be put into a ring, for fast & simple cascade.
> >
> > A cheap, simple I/O uC in DIP40, with SPI hardware, is the
> > AT89S8253. It also comes in SDIP42 (same size as DIP28).
> >
> > -jg
>
> Could u suggest me a SPI peripheral IO expansion device?
>

I think the intention was that the AT89S8253 would be the I/O expansion.
I think that this is a little overkill since it has a lot of fancy stuff
like EEPROM.
There are plenty smaller devices including the ATmega8515.
The 28 pin packages are also nice and much smaller than the 40 pin devices.

In reality you can use a development board.
The STK500/501 will provide you with a 64 pin chip and most of the signals
are
coming out on headers, so you can test most stuff on that board. 

-- 
Best Regards,
Ulf Samuelsson   ulf@a-t-m-e-l.com
This is a personal view which may or may not be
share by my Employer Atmel Nordic AB