Zilog Z80380 - Manual (Page 140)

5-106
Z380 ™
U SER ' S M ANUAL
DC-8297-03
Z ILOG
MULTW
MULTIPLY (WORD)
MULTW [HL,]src src = R, RX, IM, X
Operation: HL(31-0)
←
HL(15-0) x src(15-0)
The contents of the HL register are multiplied by the source operand and the product is
stored in the HL register. The contents of the source are unaffected. Both operands are
treated as signed, two’s complement integers.
The initial contents of the HL register are overwritten by the result. The Carry flag is set to
indicate that the upper word of the HL register is required to represent the result; if the Carry
flag is cleared, the product can be correctly represented in 16 bits and the upper word of
the HL register merely holds sign-extension data.
Flags: S: Set if the result is negative; cleared otherwise
Z: Set if the result is zero; cleared otherwise
H: Unaffected
V: Cleared
N: Unaffected
C: Set if the product is less than –32768 or greater than or equal to 32768; cleared
otherwise
Addressing Execute
Mode Syntax Instruction Format Time Note
R: MULTW [HL,]R 11101101 11001011 100100rr 10
RX: MULTW [HL,]RX 11101101 11001011 1001010y 10
IM: MULTW [HL,]nn 11101101 11001011 10010111 -n(low)- -n(high) 10
X: MULTW [HL,](XY+d) 11y11101 11001011 ——d— 10010010 12+r I
Field Encodings: rr: 00 for BC, 01 for DE, 11 for HL
y:
0 for IX, 1 for IY