In message  <01BC3401.94068C40@dialup40.eramp.net> PICLIST@MITVMA.MIT.EDU
 writes:
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> Hi all,
> My question pertains to the use of other microcontrollers.
> Why is the MicroChip PIC controller so much better than other =
> controllers like ATMEL or ZILOG? Is there an application that would be =
> better suited to one of the other manufacturers? I am kind of new to the =
> microcontroller world and I see that there are quite a few =
> manufacturers. On what grounds do these companies compete? I really just =
> want verification that I have gotten lucky and chosen the best =
> controller out there.

Troy,

There is always the new Atmel AVR microcontroller. The AT90S1200 is
supposed to be available now, but I have yet to get hold of one.

Being EEPROM based, it seems to be aimed directly in competition
with the 16C84. It has several features that make it more attractive
than an 16C84 and other PICs in general.

  o a richer instruction set, 87 instructions including an add
    with carry.

  o 32 w registers. The end of the w reg bottle neck. And you can
    access 2 registers in one instruction. eg add r1, r2.

  o Single clock cycle instruction execution for most instructions.
    The PIC divides its clock by for for each instruction. On
    this basis, for a given clock frequency, the AVR is roughly 4
    times faster than a PIC.

  o 24MHz max clock speed. Compared to 10MHz for a C84. This is
    nearly two and a half times quicker and when combined with
    the single cycle instruction execution and the richer instruction
    set makes for something in excess of 10 times the speed.

  o Analogue comparator.

  o 20 pins - 2 extra i/o per package.

  o Direct reads of the port pins rather than a register aimed at
    overcoming the read-before-write problem on PICs.

  o Different interrupt vectors for different interrupts.

Future 20 pin AVRs will have more counters, PWM and UART. 40 Pin
versions are on the cards.

Things I've found from the data sheets which aren't as good as the
PIC are:

  o The watchdog can be switched off by your application. This seems
    crazy to me.

  o There is no way to differentiate between a POR reset and a watchdog
    reset.

  o The I/O pins can only sink reasonable currents.

  o There is no RC oscillator option.


I understand that Atmel isn't the only company bringing out chips
like this, and wonder if Microchip have something up their sleeves
which would wipe the floor with an AVR.

I checked the prices, about  1.50 UKP for 100 off. Less than I pay
for 16C84, more than the 15C56.

Any comments from the Microchip guys on this list?


Regards,


Mike Watson