Microchip PIC Forum: Re: [piclist] address decode on serial

Wednesday, November 28, 2007

Re: [piclist] address decode on serial

You don't need to do that with the newer PICs. Read up on "9th bit
addressing" for the PIC. In this mode the 9th bit is set and the USART
recognizes this as an address. Your code then needs only to look for this
bit set to pay attention to a byte as an address.

DLC

> Hello all:
>
> I have a desire for a project to use a PC as a master, poll various
> pics on a rs485 network, using a very simple polling idea and have
> the pics respond with their status as well as take data from the pic
> if desired.
>
> Im working on this in small parts and my first thoughts on overall
> programming is this to get the pic to respond to its address:
>
> pic watches the data stream for a "sync byte" such as "89"
> if "89" appears then check the next byte for its address such as "02"
> if "02" is its address then respond with its status
>
> I tried this before without using the sync byte and the pic
> responded to any bit sequence that appeared and matched 4 bits. By
> using the sync byte, will this help with the false responses? my
> first attempt was using a addres of "2" and any bit opattern that
> matched "0010" falsed a response.
>
> Serial speed is not set, I tested at 9600.....
> PIC is 16F627/16F628
>
> Im a NOVICE to programming and trying to learn as I go here.
>
> All help appreciated!
>
> Randy
> kk4ej
>
>
>
>
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--
Dennis Clark
TTT Enterprises