Nicolas Souchu (
Wed, 9 Dec 1998 22:28:39 +0000

On Tue, Dec 08, 1998 at 11:53:57PM +0000, Tim Waugh wrote:
>On Wed, 9 Dec 1998, Nicolas Souchu wrote:
>> >The only reason it would be necessary is if the peripheral ONLY speak ECP
>> >mode, and we don't have the hardware for it.
>> Then, the peripheral is not IEEE1284 compliant.
>I meant for the reverse channel -- it might only speak compatibility mode
>and ECP mode. Software-emulated ECP-write is only really justifiable with
>your examples:

NIBBLE mode is mandatory for the Device-ID sequence.

>> But,
>> - peripheral behaviour may be easier to analyze with emulation
>> (OfficeJet development is an example)
>> - when 2 hosts exchange data, one of them, with full ECP support,
>> may want to take advantage of DMA+hardware_handshake
>> - just for fun

These examples justify ECP-reads too. All-in-one devices have scanners that
do mostly ECP-reads.

>For some reason, the SPI in 1284-1994 says that the list of modes that
>SPI_IO understands (for its 'mode' parameter) includes both ECP and
>ECP-with-software-emulation. Weird.

I haven't read it in depth yet. Could this interface stand for a common
interface to FreeBSD and Linux? This would hide our differences and let
us share drivers, at least in ECP mode.

>> BTW, Tim, did you think about host<->host operations? The main issue is
>> reverting the negociation with only 4 control lines against 5 status lines.
>I hadn't, but the idea intrigues me. I'll have to draw myself some
>pictures from your wiring scheme.
>> I talk to you about this in order to get FreeBSD<->Linux _compatible_
>> for an ECP/EPP-IP interface.
>Excellent plan. I'm sorry to say that I haven't been following FreeBSD
>development with ppbus. Thanks for the link, btw.

Ok, I'm glad to get your approbation. I cc some interested people on the
FreeBSD side.

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FreeBSD - Turning PCs into workstations -

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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:53 EST