Hi Microchip!

I think I have an idea that could do mega cool things for your PIC range
(84 in particular)

Simply, add a hardware shift register on chip which is programmed via a
register.

For clarification, firstly lets assume an 8 bit shift register:

Now, the speed of the shifting is controlled by a divider connected to
the main clock, and is set by a register.  Also, a bit indicates if the
input to the register comes from an external source, a simple MSB->LSB or
just filled with zeros.

What is the use, you may ask?

Well, with such a system, you could quite easily make PWM, by setting the
bits on as the duty cycle, choosing the required divider for frequency
and using MSBLSB wrap around.  The result?  You've got a good PWM which
can be tied to a motor control or low pass filtered to make audio.

Another usage of the shift register could be an Inter-PIC communication
system, simply fill the register with data a let it blast out. Also, a PCM
system effectively on chip.

Now, I mentioned that the shift register could also take information
externally.  Well, here is something that might interest people....

Hook up a sigma-delta converter (two op amps), and you get a 1 bit output
stream which could be fed into the PIC.  Result?   An A/D!  If you are
wondering, such a system requires a higher bandwidth.  For instance, if
you want to read in an analogue signal at the nyquist rate at 8 bits of
accuracy, your sample rate becomes 8*nyquist, accepting digital input.
By putting in a simple software digital decimation filter, this means
you've got an 8 BIT A/D converter!!!!  No flash circuitry, no successive
approximation, real simple, good accuracy, and it works.


[  COOOL  HUH!?!?!?!   ]

Now, to take the example further, and to where I think MICROCHIP should
take it to:

Give the PICS two such shift registers, a hook them up so one shift
register can either get information from intself, and external pin, a
zero or the other shift register.

This would give the PIC the option of either two shift registers, or one
16 bit shift register.

The 16 bit register could mean that you have a PWM, a PCM system, a 16
bit D/A or alternately a 16 bit A/D.

Also means that you could blit out information, then read in information
as the register is simultaneuosly filled with incoming information.

For a low complexity, low cost addition, it's pretty neato.

Catcha,

Regards,
        Mick Kunstelj.


-------------------------------------------------------------------
 Greetings and Salutations from Mick Kunstelj    |If MS ever do make a global
   u913596@student.canberra.edu.au               |network, you should be more
                                                 |worried about a satellite
 I accept no care or responsibility for anything,|landing on you than them
 anywhere or anytime.... So NYAH!!!!             |taking things over...
-------------------------------------------------------------------