Xiaofan Chen wrote:

> Two things:
> 1) Are you saying you want to use FBD to programing PICs?
> Even though this might be possible but I highly doubt it will be
> popular anytime soon. Last time there was a ladder compiler
> for PIC but I never really know if the product comes out or not.

I doubt that you will see a ladder compiler used with PIC to
build a FBD but ST or possibly IL might be a a reasonable
way to program PIC's

> 2) Are you saying you want to use mid-range as a part for
> the distributed control unit? Something like those mentioned
> in IEC61499.

The is the approach that I see as a possibility. Small functional
blocks either distributed or in one place. For example a sensor
that deals with its calibration data and signal processing having
a FBD interface to the rest of the system. Well defined standard
interfaces.

> I used to see 8-bit MCUs like 8051 used in small PLCs.
> Now even the cheapest US$100 pico/nano PLC uses 32bit
> MCU.

A system now is a pico PLC with external links to IEC61499
type FBD's or other pico PLC

> And even if you are right, the ability of the enhanced PIC16F
> has already been available in PIC18F for years. And none of
> the things come close to what you think have come into reality.

True but there is a lot of work now on distributed processing and
on the ISO61131 and ISO61499 standards. As an alternative to
RTOS's in small embedded systems event driven programming
works well.

I have done a lot of work in tools support for automotive engine
controllers. Most of them use a multiprocessor based event
system consisting of a powerPC sized host CPU and two
I/O event driven processors. The operation is surprisingly similar to
ISO/IEC 61499. There is no RTOS in the host CPU.

Regards

--
Walter Banks
Byte Craft Limited
http://www.bytecraft.com








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