Re: [PARPORT] ECP mode

Thomas Sailer (
Mon, 19 Oct 1998 10:25:44 +0200

Daniel E. Ungar wrote:

> I must, right off, confess that the FPGA-implemented port on our x-ray
> spectrometer is not at all *compliant* with any revision of the IEEE 1284
> spec'. It merely implements the barest essentials of single-peripheral
> ECP mode, and if the host does not support that, it cannot in fall back to

I'm in *exactly* the same position :-) And since I also have to
the FPGA bitstream in SPP mode, it does not make much sense to implement
negotiation, as the host knows what the firmware can do it downloads.

So there's definitely a need to bypass most of IEEE 1284 ECP, esp.

How about structuring the negotiation functions as a kind of "library",
so the device drivers (such as lp) can use them if they want?

> What we *do* need is true DMA operation for a data stream of at about
> 750 KBytes/sec. Any per-byte response to IRQ, or, worse yet, device
> polling,

I'm currently using EPP, but the communication overhead is huge

BTW: It seems that although the ECP protocol could do it, in most
implementations the host cannot force a direction change
from backward to forward without possible data loss.
How did you solve this problem? Just avoid it?

> Can anyone point me to a Linux driver that illustrates the use of DMA?

More specifically: ISA DMA. There's for example
sound (DMA functions in DMAbuf.c and audio.c), floppy.c,
soundmodem (smdma.h), hfkernel


-- To unsubscribe, send mail to: --
-- with the single word "unsubscribe" in the body of the message. --

This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:37 EST