Harold, If it's a really old motherboard, it may not have bidirectional hardware. A lot of the old systems used unidirectional hardware for teh pritner ports, since they were output only. The only BIOS calls I have documented and/or could find references to are as follows: INT 0x17, AH=0x00, AL = , DX = LPT# -- Write character INT 0x17, AH=0x01, DX = LPT# -- Initialize port INT 0x17, AH=0x02, DX = LPT# -- Status request On return from INT17, AH contains printer status: Bit: Meaning: 0 Timeout 1 RESERVED 2 RESERVED 3 I/O Error 4 Selected 5 Out of paper 6 Acknowledge 7 Not Busy This is from an OLD (AT vintage) reference manual. It is interesting to note that Microsoft wants this whole thing completely de-suppotred... to meet tehir "legacy-free" specification (http://www.microsoft.com/hwdev/NewPC/LF.htm), INT17 is not even a requirement -- because LPT ports are verboten, as are serial pots and floppy drives. Where the hell do these people get their crazy pills? Anyway, I suspect that any support for bidirectional modes are provided only in the drivers for the printers and depend on the EPP/SPP or whatever hardware being present. If I'm wrong and the BIOS in a newer system does support the other modes or provides input functions, I can't find it documented anywhere. Dale On Mon, 27 Aug 2001, Harold M Hallikainen wrote: > Yes but... that's not using a BIOS call. I'm trying to avoid bit banging > in my code (by handing it off to bios). INT17, function 00 sends the > contents of AL to the printer and takes care of all handshaking. I'm > looking for a similar call to read stuff back in byte mode (or PS/2 > mode). > > Thanks! > > Harold > > > On Tue, 28 Aug 2001 09:11:03 +1000 David Huisman > writes: > > Assembly.. > > > > I think you'll find it is "in" and "out". > > > > From memory, the DX register is used to pass the address of the port > > and AX > > used for data. (you can retrive 8-bit data from AL register). I > > think it > > goes something like. > > > > DX = $3f8 (your port address) > > AX = in(DX) > > Data = AL > > > > and.. > > > > DX = $3f8 > > AL = Data > > out(DX) > > > > In C it is like... > > > > a = (inportb(STATUS) & 0xF0); > > > > check out http://www.beyondlogic.org/spp/parallel.htm > > > > I can check up on this later today if you have not got the info you > > need by > > then > > > > Regards > > > > David Huisman > > > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Andy N1YEW > > Sent: Tuesday, 28 August 2001 4:05 > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [PIC]: BIOS call to read from bidirectional parallel > > port? > > > > > > Is this in assembler or c? > > > > x=inb(port); > > outb(port,x); > > > > dont hold me to the inb and outb syntax... check it yourself... > > > > that should work.. > > ----- Original Message ----- > > From: "Harold M Hallikainen" > > To: > > Sent: Monday, August 27, 2001 1:58 PM > > Subject: [PIC]: BIOS call to read from bidirectional parallel port? > > > > > > > I'm using PSP mode on a PIC to interface to a PC parallel > > port. In > > the > > > PC application, I'm using BIOS interrupt 0x17 to send stuff to the > > PIC > > > thru the parallel port. My BIOS book is real old (1991) and make > > no > > > mention of bidirectional parallel ports. Is there a STANDARD BIOS > > call to > > > read from a parallel port? > > > > > > Harold > > > > > > > > > FCC Rules Online at http://hallikainen.com/FccRules > > > Lighting control for theatre and television at > > http://www.dovesystems.com > > > > > > ________________________________________________________________ > > > GET INTERNET ACCESS FROM JUNO! > > > Juno offers FREE or PREMIUM Internet access for less! > > > Join Juno today! For your FREE software, visit: > > > http://dl.www.juno.com/get/tagj. > > > > > > -- > > > http://www.piclist.com hint: The PICList is archived three > > different > > > ways. See http://www.piclist.com/#archives for details. > > > > > > > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > > FCC Rules Online at http://hallikainen.com/FccRules > Lighting control for theatre and television at http://www.dovesystems.com > > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > http://dl.www.juno.com/get/tagj. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- A train stops at a train station. A bus stops at a bus station. On my desk I have a workstation... -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.