The source register in the OUT instruction is:
Ch 09: Software Interrupts and DOS/BIOS Services
Covers IVT structure (256 vectors x 4 bytes each = 1KB), pushing flags and CS:IP during interrupt invocation, hooking existing software interrupts, and invoking DOS function calls for disk and character I/O.
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CS401 - Computer Architecture and Assembly Language Programming Examination Practice
Timed practice exam simulation for CS401 - Computer Architecture and Assembly Language Programming.
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Which of the following pins of the parallel port are grounded?
Which of the following IRQ lines is designated as the cascading interrupt?
Provide valid x86 assembly instruction(s) to read an 8-bit value from I/O port number 0x312.
Provide valid x86 assembly instruction(s) to write the 8-bit value of the AL register to I/O port address 0x12.
Which of the following hardware IRQs functions as the cascading interrupt line between the Master and Slave 8259 Programmable Interrupt Controllers (PIC)?
In hardware interrupt processing, an End of Interrupt (EOI) command signal is sent to the 8259 PIC by which component?
Explain the purpose and working of the following assembly code segment. Also, write instruction-level comments describing the purpose of each instruction:
[org 0x0100]
jmp start
count: dw 0
attribute: dw 0x07
second: dw 0
timer:
push di
push cx
push ax
push es
inc word[cs:count]
cmp word[cs:count], 91
je clrscr
jmp exit
Explain the purpose and line-by-line working of the following TSR (Terminate and Stay Resident) interrupt service routine and initialization code segment. Also, write instruction-level comments for each line:
clrscr:
mov word [cs:count], 0
mov ax, 0xb800
mov es, ax
xor di, di
mov al, 0x20
add word [cs:attribute], 0x10
cmp word [cs:attribute], 0x77
jbe next
mov word [cs:attribute], 0x07
next:
mov ah, [cs:attribute]
mov cx, 2000
cld
rep stosw
exit:
mov al, 0x20
out 0x20, al
pop es
pop ax
pop cx
pop di
iret
start:
xor ax, ax
mov es, ax
cli
mov word [es:8*4], timer
mov [es:8*4+2], cs
sti
mov dx, start
add dx, 15
mov cl, 4
shr dx, cl
mov ax, 0x3100
int 0x21
Which hardware component interrupts the system 18.2 times per second in x86 architecture? Explain its mechanism and list some of its primary practical uses.