|From what I understand, if you have a ECP or EPP port, it still acts as a
SPP port. The PC and the remote device have to negociate higher levels.
If you don't negociate, it is a SPP port. I think it is covered in
documents on the Microsoft Development Platform CD's. We looked into this
some time ago, and decided to go for 'nibble' data transfers into the PC
from a PIC using 5 input lines and 2 input lines using SPP mode:
Input: 4 'data' lines for nibble transfers. They aren't the real data
lines, we use SPP control lines.
Output a strobe line to show PC is ready for the second nibble. Interrupts
can take a while to service.
a test request line hat we use to make sure the PIC is really there. It
sends back 0x00 and 0xff,
which makes a good port/wiring test
We had real fun adding opto-isolators, which take longer to pass a '1' than
a '0'. This can really mess up a transfer. We clear the IRQ line to show
the second nibble is on the port, so if you do it all at the same time, the
IRQ line clears at the PC before the data bits get there.
<sni.net> Ed Todd edtodd
With all the questions on parallel ports, I figured I throw in a question
Does anybody have any source for a PIC serial-to-parallel converter. I
need to make a smart printer interface to connect an SCO UNIX box to an old
Tandy printer, and do some conversions in the process. I'll be connecting
to a multi-serial port (MAXPEED I think) on the PC using h/w and/or s/w
handshaking, and the parallel port to the printer.
Hey, I'm willing to swap library stuff here, too.
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
Hardware & Software for Industry & R/C Hobbies
"Go fast, turn right, and keep the wet side down!"
Didnt Mchip publish one in an early issue of the ECH if my memory is corect ?
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