INSTRUCTION SET DESCRIPTIONS

Table C-4. Instruction Set (Continued)

Name

Description

Operation

Flags

Affected

 

 

 

 

 

 

 

XLAT

Translate:

AL ((BX) + (AL))

AF –

 

XLAT translate-table

 

CF –

 

 

DF –

 

Replaces a byte in the AL register with

 

 

 

IF –

 

a byte from a 256-byte, user-coded

 

 

 

OF –

 

translation table. Register BX is

 

 

 

PF –

 

assumed to point to the beginning of

 

 

 

SF –

 

the table. The byte in AL is used as an

 

 

 

TF –

 

index into the table and is replaced by

 

 

 

ZF –

 

the byte at the offset in the table corre-

 

 

 

 

 

sponding to AL's binary value. The first

 

 

 

byte in the table has an offset of 0. For

 

 

 

example, if AL contains 5H, and the

 

 

 

sixth element of the translation table

 

 

 

contains 33H, then AL will contain 33H

 

 

 

following the instruction. XLAT is

 

 

 

useful for translating characters from

 

 

 

one code to another, the classic

 

 

 

example being ASCII to EBCDIC or

 

 

 

the reverse.

 

 

 

Instruction Operands:

 

 

 

XLAT src-table

 

 

 

 

 

 

XOR

Exclusive Or:

(dest) (dest) xor (src)

AF ?

 

XOR dest, src

(CF) 0

CF

 

(OF) 0

DF –

 

Performs the logical "exclusive or" of

 

 

IF –

 

the two operands and returns the

 

 

 

OF

 

result to the destination operand. A bit

 

 

 

PF

 

in the result is set if the corresponding

 

 

 

SF

 

bits of the original operands contain

 

 

 

TF –

 

opposite values (one is set, the other

 

 

 

ZF ¸

 

is cleared); otherwise the result bit is

 

 

 

cleared.

 

 

 

Instruction Operands:

 

 

 

XOR reg, reg

 

 

 

XOR reg, mem

 

 

 

XOR mem, reg

 

 

 

XOR accum, immed

 

 

 

XOR reg, immed

 

 

 

XOR mem, immed

 

 

 

 

 

 

NOTE: The three symbols used in the Flags Affected column are defined as follows:

the contents of the flag remain unchanged after the instruction is executed ¸? the contents of the flag is undefined after the instruction is executed

the flag is updated after the instruction is executed

C-47

Page 370
Image 370
Intel 80C188XL, 80C186XL user manual Translate, Xlat translate-table, Exclusive Or, XOR dest, src