Re: Flow Controlled UART problem

fatih_lokumcu wrote:

> I want to know if anyone has implemented a flow controlled UART with
> mpc555. The sci's do not support flow control but I thought of using
> TPU UART function together with TPU DIO functions. I am planning to use
> TPU DIO to implement RTS and CTS signals. Do you thing it is logical to
> to this way? Has anyone got a similar problem before?

I've written a TPU UART function that handles flow control in the TPU 
along with double buffering and a few other features.  If you can write 
microcode, it's not too hard to modify the transmit portion of the UART 
to check the state of a CTS input on another channel and delay the start 
of a transmit.  The CPU can then easily manage RTS using the vanilla DIO 
function.

Since with the free UART, the CPU already has to be involved with each 
character handled, it's not much of an extension to have it check the 
state of a CTS input and manage an RTS output.  You have to decide 
whether the CTS will cause an interrupt when it's asserted or you just 
poll it from time to time.  The choice between this and the microcode 
approach depends on the device you're talking to and your system 
requirements.  Some older unbuffered serial devices drop CTS for every 
character received.  That might be more of an interrupt load than you 
want to contend with.

-- 
Eric McRae, Electro-Logic Machines, Inc.
511 Root St., Port Townsend WA, 98368
Phone/Fax: 360.379.0969, http://www.elmi.com



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