RE: [Patch] new serial flow control

["Stuart MacDonald" <stuartm@connecttech.com>]

From: Alan Cox
> On Mer, 2004-10-06 at 08:38, Samuel Thibault wrote:
> > No: CRTSCTS is a one-signal-for-each-way flow control: each
> > side of the link tells whether it can receive data. CTVB is a
> > two-signals-for-only-one-way flow control: the device tells when it
> > wants to send data, the PC acknowledges that, and then one frame of
> > data can pass.
> 
> This sounds a lot like RS485 and some other related stuff. I need to
> poke my pet async guru and find out if they are the same thing. If so
> that would be useful.

RS485 is a driver-transparent electrical interface. Unfortunately the
half-duplex and master-slave(s) arrangements require some sort of
token passing to know when they can successfully transmit. This is
usually handled by the apps in some manner, although it's often wanted
to be handled by the serial driver. This could be one method of
signalling, but isn't sufficient to show RS485 operation.

I haven't seen this style of flow control before. What uses it?

..Stu