AMD Am186 Series, Instruction Set

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Instruction Set 4-6
AAM ASCII Adjust AL After Multiplication AAM
What It Does
AAM converts an 8-bit unsigned binary number—ordinarily the product of two unpacked
decimal (BCD) numbers—to its unpacked decimal equivalent.
Syntax
Description
Use AAM only after executing the MUL instruction between two unpacked BCD operands
with the result in the AX register. Because the result is 99 or less, it resides entirely in the
AL register. AAM unpacks the AL result by dividing AL by 10, leaving the quotient (most
significant digit) in AH and the remainder (least significant digit) in AL.
Operation It Performs
Flag Settings After Instruction
Examples
This example multiplies two unpacked decimal digits.
Form Opcode Description
Clocks
Am186 Am188
AAM D4 0A ASCII-adjust AL after multiplication 19 19
AAM
/* convert AL to decimal */
AH = AL / 10;
AL = AL % 10;
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Processor Status
Flags Register
reserved
OF DF IF TF SF ZF AF PF CF
? = undefined; – = unchanged
SF=1 if result is 0 or positive
SF=0 if result is negative
ZF=1 if result equal to 0
ZF=0 if result not equal to 0
PF=1 if low byte of result has even number of set bits
PF=0 otherwise
? – – – res ? res res ?
UMULTIPLICAND DB 07h ; 7 unpacked BCD
UMULTIPLIER DB 06h ; 6 unpacked BCD
; multiply unpacked decimal numbers
MOV AL,UMULTIPLICAND ; AL = 07h = 7 unpacked BCD
MUL UMULTIPLIER ; AL = 2Ah = 42
AAM ; AX = 0402h = 42 unpacked BCD