BBS: Inland Empire Archive
Date: 02-04-93 (07:00) Number: 371
From: JERRY HUNTER Refer#: NONE
To: CALVIN FRENCH Recvd: NO
Subj: Modem INP & OUT ports Conf: (2) Quik_Bas
> Hi! I'm new to this echo, but what I'm wondering is how I
> can access the _other_ com ports (3 & 4). OPEN "COM4 etc.."
> or OPEN "COM3 etc.."
Calvin :
INP and OUT are not required.
The following example moves the Base Port Address of COM3 (as provided in the
BIOS Data Area @ Offset &H40) into the slot reserved for
COM1:. Following the execution of this code snippet, you
may OPEN COM1:, and what you actually have is COM3. The
technique is referred to as "Device Aliasing", and can be
used to substitute COMx: ports, LPTx: ports, etc...
DEFINT A-Z
DEF SEG = &H40
OLDCOM1%= PEEK(1)*256 OR PEEK(0)
OLDCOM3%= PEEK(5)*256 OR PEEK(4)
POKE 0,OLDCOM3% MOD 256
POKE 1,OLDCOM3% \ 256
Do NOT forget to switch the values BACK before your program
terminates, lest you FUBAR the user's COMx: port (PCPlus,
Telix, etc. will be unable to find COM1:, and will
subsequently access COM3 whenever COM1 is referenced (G).
This technique is acceptable when attempting to access COM3
and COM4, provided you are NOT trying to access ALL 4 COMx:
ports concurrently. If THIS is the case, you will need to
A) Use a Fossil, or B) write your own driver in C or MASM.
Hope it helps...
Regards,
J.Hunter
--- GEcho 1.00/beta
* Origin: DarkStar - QB45 Comes ALIVE! - (501) 631-5976 (1:391/2090)
