Re: [PARPORT] ecp (8bit) nullmodem cable pinout?

Nicolas Souchu (
Wed, 3 Feb 1999 23:23:00 +0100

On Mon, Feb 01, 1999 at 08:48:20AM -0200, Rafael Rodrigues Obelheiro wrote:
>On Sun, 31 Jan 1999, Andree Borrmann wrote:
>> is there a standard for ecp 8bit nullmodem cables?
>> How exactly are the status and control lines connected?
>> If someone can answer these question I would volunteer to rewrite the plip
>> driver to support 8bit modi.
>I've been working on this stuff for a couple of weeks. I hope I'll be able
>to deliver a working driver by the end of the month. So far, I've been
>finding out several undocumented "features" of ECP (or, at least, of this
>implementation of ECP), which is rather time-consuming. Right now, I have
>a couple of programs that perform host-to-host communication in ECP mode,
>but I'm still devising a suitable protocol (to control channel reversion)
>so that a real PLIP-ECP driver can be written.

Yeah! And what's your idea about negociation?

>As for the wiring, I'm using
> 100R
> D0-D7 ------/\/\/\------ D0-D7
> HostClk -----------------> PeriphClk
> PeriphClk <----------------- HostClk
> HostAck -----------------> PeriphAck
> PeriphAck <----------------- HostAck

>ReverseRequest ---+-------------> X-Flag
> AckReverse <--|
> X-Flag <-------------+--- ReverseRequest
> |--> AckReverse
> 1284 Active -----------------> PeriphRequest
> PeriphRequest <----------------- 1284 Active

I do not agree with your wiring :)

I think, PeriphRequest should be connected to ReverseRequest and
1284 Active to X-Flag. Otherwise, byte mode handling is incompatible with
IEEE1284 and you may not be able to handle ECP recovery either in a host to
host transfer mechanism.

>but this is still subject to change, since I've been experiencing some
>tough problems.
>Rafael Rodrigues Obelheiro
>Rio Grande, RS, Brazil

Let's Tim CC you our last mail about ECP. We aim at having something compatible
between FreeBSD and Linux.



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