Specifications
D:\D\inter61a\INTERRUP.A Saturday, January 08, 2011 11:31 AM
on PS/2s, COM2 through COM8 share this interrupt; on many PC's, COM4
shares this interrupt
may be masked by setting bit 3 on I/O port 21h
DOS 3.3+ revectors IRQ3 to a stack-switching routine unless STACKS=0
has been set in CONFIG.SYS. MS/PC-DOS use the IBM Interrupt Sharing
Protocol (see #02568) when hooking this IRQ
SeeAlso: INT 0C"COM1",INT 53"DESQview",INT 5B"DoubleDOS",INT 7B"GO32"
--------C-0B---------------------------------
INT 0B CP - CPU-generated (80286+) - SEGMENT NOT PRESENT
Desc: generated when loading a segment register if the segment descriptor
indicates that the segment is not currently in memory, unless the
segment is an LDT (see INT 0A"CPU") or stack segment (see
INT 0C"CPU") needed by a task switch
Note: may be used to implement virtual memory by loading in segments as they
are accessed, clearing the "not present" bit after loading
SeeAlso: INT 0A"CPU",INT 0E"CPU"
--------h-0B---------------------------------
INT 0B - HP 95LX - LOW-LEVEL KEYBOARD HANDLER
Desc: this is the lowest-level keyboard handler on an HP 95LX palmtop
Note: debounces key, places the keycode in I/O register 60h, and calls INT 09
SeeAlso: INT 09,INT 0D"HP 95LX",INT 15/AX=4DD4h
--------H-0C---------------------------------
INT 0C C - IRQ4 - SERIAL COMMUNICATIONS (COM1)
Desc: automatically asserted by the UART when COM1 needs attention, if the
UART has been programmed to generate interrupts
BUG: this vector is modified but not restored by Direct Access v4.0, and
may be left dangling by other programs written with the same version
of compiled BASIC
Notes: on many PC's, COM3 shares this interrupt
may be masked by setting bit 4 on I/O port 21h
DOS 3.3+ revectors IRQ4 to a stack-switching routine unless STACKS=0
has been set in CONFIG.SYS. MS/PC-DOS use the IBM Interrupt Sharing
Protocol (see #02568) when hooking this IRQ
SeeAlso: INT 0B"COM2",INT 54"DESQview",INT 5C"DoubleDOS",INT 7C"GO32"
--------C-0C---------------------------------
INT 0C C - CPU-generated (80286+) - STACK FAULT
Desc: this interrupt is generated in protected mode on a stack overflow or
underflow, or if an inter-level transition or task switch references
a stack segment marked "not present"; it is generated in real mode
on accessing a word operand at SS:FFFFh
Note: the 80286 will shut down in real mode if SP=1 before a push. On the
-21-
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