BABYL OPTIONS: Version: 5 Labels: Note: This is the header of an rmail file. Note: If you are seeing it in rmail, Note: it means the file has no messages in it.  0, unseen,, *** EOOH *** From: ochealth@unixg.ubc.ca (ochealth) Newsgroups: comp.os.os2.misc,comp.sys.ibm.pc.hardware,comp.os.msdos.misc Subject: Re: Question about Parallel Port, please read Date: 28 Dec 1992 23:03:38 GMT Organization: University of British Columbia, Vancouver, B.C., Canada NNTP-Posting-Host: unixg.ubc.ca In article pjh@mccc.edu (Pete Holsberg) writes: >In article <1hmba2INN7jk@iskut.ucs.ubc.ca> ochealth@unixg.ubc.ca (ochealth) writes: > >=>If I set the jumper for bidirectional operation, am I depending on the >=>printer electronics to set that bit correctly? Do all printers do it >=>correctly? > >=There are three ports that control the printer port: >=for lpt1, there is port 378h (data) and 379h and 37Ah for other stuff. >=Since bit 5 is assigned at 379, and bit 5 isn't used for 37A, I guess >=the control bit is at port address 37A. > >True, but that doesn't answer the question. Do you know of any programs >that control those ports? Thanks. Since bit 5 of the control reigister ( 37Ah for LPT1) is non-standard, I doubt if many programs will. The bidirectional feature will be useless for printer stuff, but since you can use the parallel port for other things, like File Shuttle (transfer files between computers) and for add on SCSI adapters, tape drives, hard disks, etc., those drivers MAY know about non-standard features, it might be usefull. Basically, if you are just putting a printer on the port, it won't matter. If you put a tape drive on the parallel port, the biderctional feature will be VERY good (I'm pretty sure the driver program will test for bidirectional ports, and WILL use them if it can.) I wrote a short C program to test out the parallel ports, and my parallel port control register doesn't let you set or clear bit 5 (or 6 or 7); BUT I noticed that several parallel port lines marked OUTPUT are actually bidirectional by default. I would leave your IO card jumpered for bidirectional ablility unless your printer acts strangely (it can't hurt). The parallel port is pretty verssatile for electronics hacking if you like doing that. It runs at 5 V, TTL logic levels, and the outputs can drive 70 mA per output pin, around 30 mA for bi-directional pins. Some of this is hardware dependent, so don't take my card's setup as gospel truth for IBMs. -- ______________________________________________________________________________ ochealth@unixg.ubc.ca