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RS485 documentation: add 16C950 UART description 

Add a notion about 16C950 UART, that is using DTR signal for RS485 mode.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Yegor Yefremov 2010-11-22 11:06:32 +01:00 committed by Greg Kroah-Hartman
parent a4fb0b228e
commit de6f86ce51
1 changed files with 5 additions and 4 deletions
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Documentation/serial/serial-rs485.txt
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@ -11,10 +11,11 @@
2. HARDWARE-RELATED CONSIDERATIONS
Some CPUs (e.g., Atmel AT91) contain a built-in half-duplex mode capable of
automatically controlling line direction by toggling RTS. That can used to
control external half-duplex hardware like an RS485 transceiver or any
RS232-connected half-duplex device like some modems.
Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in
half-duplex mode capable of automatically controlling line direction by
toggling RTS or DTR signals. That can be used to control external
half-duplex hardware like an RS485 transceiver or any RS232-connected
half-duplex devices like some modems.
For these microcontrollers, the Linux driver should be made capable of
working in both modes, and proper ioctls (see later) should be made