piclist 1997\08\11\165402a >
Thread: New PICs and Architectures
picon face BY : John Payson email (remove spam text)

> (1)
> Its more than just extra I/O pins.
> You overlook the fact that for most
> low-end applications, a microcontroller
> spends precious clocks and program memory
> to scan and debounce a keypad, or send
> data to a multiplexed LED display.
> Just imagine, if the hardware takes care of
> this, the cpu can take care of more
> number-crunching tasks, and even the interrupts
> can be put to better use.

Keeping a display and keyboard scan running at 100Hz each requires the
expenditure of less than 10,000 cycles per second.  If you don't have
enough CPU cycles available, boosting the speed of the chip is cheaper
than adding extra hardware.  Given that neither display scanning nor
keyboard scanning is particularly time-critical, I don't see much bene-
fit from adding automatic display scanning hardware (*).

(*) For an LCD driver, automatic scanning may allow the display scan to be
run while the CPU is asleep, resulting in substantial power savings versus
a CPU-driven scan.  LED's, however, are so power-hungry that saving 2mA by
shutting down the CPU is a non-issue if the LED's are running.

{Quote hidden}

Other companies do make such things.  Alternatively, some of the newer PICs
will have a built-in oscillator for precisely that reason.

In reply to: <9708111916.AA01454@shakti.hal.com> from "Ravindra Divekar" at Aug 11, 97 12:16:05 pm
See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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