Disk not ready, and gene

 BBS: Inland Empire Archive
Date: 03-25-93 (11:32)             Number: 333
From: DIK COATES                   Refer#: NONE
  To: ROBERT CHURCH                 Recvd: NO  
Subj: Disk not ready, and gene       Conf: (2) Quik_Bas

>>>> QUOTING Robert Church to All <<<<

 RC> isn't there the system locks up!  I don't wan't to use error trapping

I don't know how you can do it in BASIC... but the routine I use with my
asm based basic library does the following...

.Code

oldint      dw    ?                        ;variable stashed in CS
buff80      db    80 dup(?)                ;80 byte buffer for strings



DisableInt  MACRO
            mov   ax, 3524h                ;DOS get int 24h vector
            int   21h
            mov   ax, es:[bx]
            mov   cs:oldint, ax
            mov   byte ptr es:[bx], 00CFh  ;replace it with IRET call
            endm



EnableInt   MACRO
            push  ax
            push  bx
            push  es
            mov   ax, 3524h                ;DOS get int 24h vector
            int   21h
            mov   ax, cs:oldint
            mov   es:[bx], ax              ;restore old value
            pop   es
            pop   bx
            pop   ax
            endm


             . . .


The macros work basically as follows... Int 24h is the critical error handler
address... and calling Int 35h gets the interrupt vector... The old value for
the interrupt vector is saved to 'oldint' and a new value is put in place...
00CFh... this is the machine code for and Interrupt Return.  When a critical
hardware error is encountered the call goes out to int24 and is immediately
returned to the program that had the error... in addition, and software
critical error code is generally returned as part of the failed call... The
code I use between DisableInt and EnableInt is ASM stuff... and I'm not sure
if the above macros can be converted to calls in a library... (I don't see why
they can't) For as long as the interrupt is redirected, there is no critical
hardware error capability... and it should be enabled ASAP...

Hope this helps, and doesn't really confuse you... Maybe Casey can add a
couple of comments...

Regards Dik

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