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?

Thanks!

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

Jim Granville <n...@designtools.co.nz> wrote in message news:<Vbild.1109$3...@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?

Thanks!

"terry" <l...@yahoo.com> skrev i meddelandet
news:9...@posting.google.com...
> Jim Granville <n...@designtools.co.nz> wrote in message
news:<Vbild.1109$3...@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   u...@a-t-m-e-l.com
This is a personal view which may or may not be
share by my Employer Atmel Nordic AB

terry wrote:

> Jim Granville <n...@designtools.co.nz> wrote in message news:<Vbild.1109$3...@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?

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
http://para.maxim-ic.com/compare.asp?Fam=expanders&Tree=uController&HP=Microcontrollers.cfm&ln

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

terry <l...@yahoo.com> wrote:

> And MCU with more than 40 pins always do not have DIP package so
> that PCB must be manufacured before further development.

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