As you might still remember I'm into simulating parallel port hardware on a
very low level.
So I need to know what real parallel port card hardware does.
I'll write down my understanding of the things hoping you'll correct my
misunderstandings. If I talk about "hardware" i have a pc parallel port host
hardware card/superio chip in mind, btw..
- In SPP mode the hardware will take put the data written to the data
register onto the data lines and automatically set the strobe signal for a
predefined time. Depending on configuration, the hardware will continue
sending even if the peripheral did not acknowledge the receiving, or wait for
- In PS/2 or tristate mode you can put the hardware in bidirectional mode by
toggling bit 5 of the control register. If the peripheral has some data to
send, it'll pull the ACK (PtrClk) line low to indicate that, while the host
hardware has to set autofeed (hostbusy) low before to indicate it's ready to
- In EPP mode the hardware handles the EPP handshake for me and sets the
lines depending on if i write to the data or address registers. Well - I've
no idea how I get informed about the peripheral did send something.
- In ECP mode the hardware handles ECP handshake as well as RLE encoding if
activated. I suppose the RLE decoding of data sent from the peripheral also
is done in hardware? Is it, from the viewpoint of the linux drivers, so that
they only outb their data to the data/address register and the hardware does
the rest of the job? What happens if something goes wrong? Does the hardware
send an interrupt or is the software accessing the parallel port supposed to
look into the status register from time to time?
In general the problem is that I want to use all the modes from an user mode
program that shall simulate a piece of hardware to another program which is
not aware of the fact that the hardware it accesses in fact is my simulator
program. So I need to know how real hardware behaves from the viewpoint of
linux low level parallel port drivers so my program can behave in the same
way. React on writes and reads to/from it's virtual registers in the right
way, set it's status register properly, and such.
The simulator program itseld shall also act as a bridge to the real hardware
and "transparently" connect the real hardware to the program accessing the
simulator program. So I also need to know how to access the parallel port
hardware from a linux user mode program.
I've read something about some IEEE1284 library and ppdev and other drivers
that might be of help?
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This archive was generated by hypermail 2b29 : Thu Jan 09 2003 - 12:36:34 EST