From: nngodinh AT pcn DOT net (NGO DINH Nhan) Newsgroups: comp.os.msdos.djgpp Subject: Re: reading/writing to COM ports Date: Wed, 02 Sep 1998 17:01:55 GMT Organization: Centro Servizi Interbusiness Lines: 35 Message-ID: <35ec4a73.10588573@news.pcn.net> References: <35E9747E DOT B7AEDED7 AT unb DOT ca> NNTP-Posting-Host: 194.184.70.242 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Precedence: bulk On Sun, 30 Aug 1998 12:49:18 -0300, Endlisnis wrote: > I'm quite sure that won't work, because I have a 'WinModem'. I've never been >able to get it to work from DOS. It doesn't use a standard address (like >0x110 or something). I think you should look at the Ralf Brown Interrupt List if you want to go directly to read ports and get IRQ calls. If you don't want to handle low-level code, you can modify the default BIOS settings that says which IO/IRQ a COM Port has. Ralf Brown Interrupt List says: === cut === MEM 0040h:0000h - BASE I/O ADDRESS OF FIRST SERIAL I/O PORT Size: WORD Notes: the BIOS sets this word to zero if is unable to find any serial ports at the addresses it is programmed to check at boot DOS and BIOS serial device numbers may be redefined by re-assigning these values of the base I/O addresses stored here === cut == And it means that you can modify the default COM1 port IO addres by putting in 0040h:0000h the right value. The same thing is for COM2, COM3 and COM4, that can be modified by putting the right value in the address 0040h:0002h for COM2, and just add 2 to the offset for the other 2 ports (DJGPP in flat mode need to have 400h, 402h, 404h, 406h). bye, --- NGO DINH Nhan e-mail: nngodinh AT pcn DOT net