Re: Cascade MCU

Nov 13, 2004 3 Replies
T


> 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?



Thanks!


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U

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
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J

Depends on how smart you want it to be :)

HC4094 / HC594/ HC595 are very cheap, cascadable, output only devices. HC596/HC597 are IP cascadable devices.

For more complex SPI I/O devices, look at

formatting link

The 89S8253 has a buffered SPI, and is good for easy package handling, and many IO in one place.

In the smaller uC class, Philips have the LPC91x series, which offer SPI in 14 and 16 pin tiny packages.

-jg

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H

Not strictly true. Just because the CPU doesn't come in a DIP package doesn't mean you have to make a PCB, since

a) you can use pre-built PCB made by someone else, a.k.a. "evaluation kit" if it's provided by the chip maker

b) you can use special adapter boards or sockets. They'll be more expensive than plain old DIP, sure. But still, they're out there, so you can use them.

Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.
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