On Mon, Oct 22, 2001 at 12:48:52PM +0300, Markus Vuori wrote:
> Hi,
>
> You remember me, I'm the beginner planning a HA system. :)
> So. I'm going to link pics together via RS-485 bus (using
> for example MAX487). How fast can I expect to be able to
> run the bus, 10kbps, 100kbps? I think I'll use the 16f87x
> pics which run at 20 MHz. I think the distance won't be
> the problem as the total physical length of the bus will be
> about 200-300 feet (max). Thank you.

Take a look at this graphic:

http://www.hw.cz/english/docs/rs485/diag_rs.gif

The corresponding text is found here:

http://www.hw.cz/english/docs/rs485/rs485.html

Under the heading "Maximum Data Transfer Speeds". One example quotes a
max speed of 1Mbps for a 100m cable (328 feet).

The PIC can easible handle 1Mbps. The USART maxes out at 1.25Mbps on the
20Mhz part. Check out the tables in the datasheet for more info.

BAJ

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