Chapter 6 - (๐ฃ๐บ ๐๐ฆ๐ง๐งโ) Flashcards
o Allows programmer to skip sections of program
- Jump (JMP)
o Allows programmer to make decisions based upon numerical tests
- Conditional jump
3 Unconditional Jumps
Short
Near
Far
๏ง 2-byte instruction that allows jumps within +127 and -128 bytes from the address
o Short jump
๏ง 3-byte instruction that allows jumps within +32k bytes from instruction
o Near jump
๏ง 5-byte instruction that allows jumps to any memory location within the real memory system
o Far jump
o Relative jumps
- Short Jump
o Moved with related software to any location in code segment without a change
- Short Jump
๏ง Follows the opcode
o Distance/Displacement
o Similar to short jump, only farther
- Near Jump
o Also relocatable
- Near Jump
o +- 2G in 80386
- Near Jump
๏ง Denotes relocatable jump address
o Letter R
o Obtains a new segment and offset address to accomplish the jump
- Far Jump
๏ง Obtain a far jump from label
o Far label
๏ง Appear in programs that contain more than one program file
o External labels
o Sets up instruction as indirect jump
o Address of jump is in register
- Jumps with Register Operands
o Double indirect jump
Indirect Jumps Using an Index
o Always short jumps
- Conditional jump
Conditional jump tests the following flag bits
๏ง Sign
๏ง Zero
๏ง Carry
๏ง Parity
๏ง Overflow
o Conditions tested by conditional jumps
- Conditional Set Instructions
o Set byte to 01H or clear a byte to 00H
- Conditional Set Instructions
- Combination of decrement CX and JNZ conditional jump
LOOP
Two Conditional LOOPs
LOOPE and LOOPNE
LOOPE
๏ง Loop while equal
๏ง Jumps if cx!=0 while an equal condition exists
๏ง Exits if condition is not equal or cx = 0
o LOOPE
o LOOPNE
๏ง Loop while not equal
๏ง Jumps if cx!=0 while a not-equal condition exists
๏ง Exits if condition is equal or if cx = 0
o LOOPNE
o Do not function when using Visual C++ inline assembler
- Dot commands
Two Dot commands
o .REPEAT-.UNTIL and .WHILE-.ENDW
o Causes all assembler generated statements to be listed
- .LISTALL
o Generates label @startup
- .STARTUP
o Used with a condition to begin the loop
- .WHILE
o Ends the loop
- .ENDW
- Series of instructions is repeated until some condition occurs
REPEAT-UNTIL Loops
o Defines start of loop
- .REPEAT
o End of loop which contains condition
- .UNTIL
- Subroutine, method, or function
PROCEDURE
three terms associated with PROCEDURE
- Subroutine, method, or function
- Group of instruction that performs one task
PROCEDURE
- Reusable section of the software
PROCEDURE
o Links to the procedure
- CALL
o Pushes the address of the instruction following the CALL(return address) on the stack
- CALL
o Returns from the procedure
- RET
o Removes an address from the stack so the program returns to the instruction following the call
- RET
o Procedures used by all software
- Global
o Far procedures
- Global
o Procedures used by a given task
- Local
o Near procedures
- Local
- Transfers flow of program to the procedure
CALL
o 3 bytes long
- Near Call
o First byte โ opcode
o Second and third โ displacement
๏ง +- 32k
- Near Call
o Like a far jump
- Far Call
o Call a procedure stored in any memory location in the system
- Far Call
o 5-byte instruction
o Opcode โ IP (2 & 3) and CS (4 & 5)
- Far Call
- often keyed with a number that addresses a CALL address in a lookup table
CALLs with Indirect Memory Addresses
- return instruction
RET
o removes a 16-bit number from the stack and places it into IP
o removes a 32-bit number and places it into IP and CS
RET
o externally derived from hardware signal
- hardware-generated CALL
o execution of instruction
- software-generated CALL
two types of INTERRUPT
hardware-generated CALL
software-generated CALL
also called โexceptionโ
INTERRUPT
- 4-byte number stored in the first 1024 bytes of memory when the microprocessor operates in the real mode
Interrupt Vectors
o 256 different software interrupt instructions
- INTs
o Address of interrupt vector is determined by multiplying the interrupt number by __
4
๏ง Used to call system procedures because the address of the system function need not be known
o Software interrupts
๏ง Used only with software or hardware interrupt service procedures
๏ง Pop stack data back into the IP
๏ง Pop stack data back into CS
๏ง Pop stack data back into the flag register
o Interrupt Return instruction
๏ง 80386 through Core2
๏ง Return from an interrupt service that is called in the protected mode
o IRETD
๏ง Pops 32-bit pointer from the stack
o IRETD
Interrupt operated in Real Mode
o Interrupt Return instruction (IRET)
Interrupt operated in Protected Mode
o IRETD
o Function as breakpoint
o 1-byte instruction
- INT 3
o Interrupt an overflow
- INTO
o Software that adds or subtracts signed binary numbers
- INTO
o Ends with IRET instead of RET, contents of flag register are saved on the stack
- Interrupt Service Procedure
๏ง Set interrupt flag
๏ง Places 1 into I flag bit
o STI
๏ง Clear interrupt flag
๏ง Places 0 into I flag bit
o CLI
๏ง Retrieves 8-byte return address
๏ง Retrieves the 32-bit EFLAG
o IRETQ
o STC
๏ง Set carry
o CLC
๏ง Clear carry
o CMC
๏ง Complement carry
o Monitors the hardware BUSY pin on the 80286 and 80386 and the TEST pin on the 8086/8088
- WAIT
- HLT
o Halt
o Stops the execution of software
- HLT
o THREE WAYS TO EXIT A HALT
๏ง By interrupt
๏ง By hardware reset
๏ง During a DMA operation
- NOP
o No operation
Appends an instruction and causes the LOCK pin to become logic 0
- LOCK Prefix
- ESC
o Escape
o Passes instructions to the floating-point coprocessor from the microprocessor
- ESC
o Comparison instruction that may cause an interrupt
- BOUND
o Compares the contents of any 16-bit or 32-bit register against the contents of two words of memory
- BOUND
๏ง Creates a stack frame by pushing BP onto the stack and then loading BP with the uppermost address of the stack frame
o ENTER
๏ง Reverses the process by reloading both SP and BP with their prior values
o LEAVE
