rs485 - SP490 or MAx490 Full Duplex ???

piire · Joined: 04 Mar 2009 Posts: 19

hi there,
I was wondering if full duplex rs-485 chip such as the sp490 or max490 work with ccs?

do you use the following code without the enable, you normally use with the half duplex rs485, as there is a dedicated line for tx and rx?

Humberto · Posted: Sat Sep 11, 2010 7:33 pm

piire · Joined: 04 Mar 2009 Posts: 19

the sp490 and max490 dont have DE and RE pins

the data sheet is below, the enable pins is used to determine if you can send or receive. or is the enable used to tell the complier that a rs485 ic is being used?

http://www.datasheetcatalog.org/datasheet/sipex/SP490.pdf

thanks
piire

Ttelmah · Joined: 11 Mar 2010 Posts: 19539

Yes.
There are two different 'full duplex' setups used. Humberto, is thinking I think of the 491 chip, where you still have the RE/DE pins, so that you can still have multiple master devices on the bus.
With the 490, you effectively just have an alternative 'point to point' signaling method, as a direct replacement for RS232. You can still have multiple receivers tapped onto the bus, but no ability for these other devices to transmit. The bus becomes 'single master' in each direction.
If all you want is a point to point connection between two devices, the 490, offers nice long distances, compared to RS232, but at the 'cost' of needing four wires.
It'll work just like RS232 with sch a connection, with no enable needed.

Best Wishes

piire · Joined: 04 Mar 2009 Posts: 19

Thank you for your advice, the confusion is cleared up!
regards
piire!