On Tue, Apr 18, 2000 at 06:56:18PM +0800, zhu qun ying wrote:
> I don't know whether the device support reverse nibble mode, it is
> suppose to be operated under ECP when negotiation is done. I am
> facing a timeout error at event 27, I may try to increase the
> timeout to see if it is all right.
It's taking longer than 35ms? (We wait for 40ms, ISTR)
> For the case of reverse nibble mode, the parport_read is using
> port->nibble_read_data, but when does the driver change the
> direction of the data line?
It doesn't need to, since the peripheral-to-host data is communicated
using the status lines.
ECP will need the data drivers to be switched off (i.e. reverse mode),
and that happens in parport_ieee1284_ecp_read_data (ieee1284_ops.c),
which calls ecp_forward_to_reverse.
> After reset, the parallel port should be in SPP mode, right?
For PC hardware parport_pc initialises ECP chipsets to PS/2 mode. For
other PC non-ECP chipsets it will be in whatever mode the BIOS is told
to set up.
For your port, I really don't know. ;-)
> When it is switching to reverse nibble, does it need to reverse the
> data line? or the nibble_read_data should do the reversion? Or it is
> all depends on what hardware available, and direction is controlled
> by low level driver?
It depends on whether the protocol in use requires the peripheral to
drive the data lines. For hardware which doesn't allow that, you
can't use that protocol. (That's what reverse_nibble is for.)
Tim.
*/
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