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Thread: Has anyone made their own multitasker for a PIC or SX device?
face BY : Dan Michaels email (remove spam text)

Neil Gandler wrote:
>I was considering making a crude multitasker for the PIC
>and even the SX device. Especially with SX devices with its
>blinding up-to 100MIPS speed, it would benefit from such
>a multitasking scheme.

There is an old Mchp appnote describing a rudimentary
multitasker, AN585.

The way I would do it is to create
>a number or threads that execute every interrupt cycle,
>which interval depends on the timer overflow. For example,
>an interrupt can be set to occur ever 20us. And if there are
>32 threads, each thread would excute every 640us.

What you are describing here is the basic idea underlying
the Scenix VPs - virtual peripherals. TImer overflows every
6 usec or so, and a divider on each process counts down the
interrupts to determine when the process should run/etc.

The big problem you encounter with the scenix, IMO, is that
even with its high performance, it still bogs down when the
#processes starts to grow.

- danM

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See also: www.piclist.com/techref/ubicom/devices.htm?key=sx
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Subject (change) Has anyone made their own multitasker for a PIC or SX device?

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