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MUL     Multiply     Rabbit 2000/3000/4000/5000 Instruction

Opcode	Instruction	Operation
F7	MUL	HL:BC = BC · DE

Clocks	8-Bit Access	16-Bit Unaligned	16-Bit Aligned
Rabbit 2000/3000/4000	12	n/a	n/a
Rabbit 5000	12	12	12

Flags				ALTD			IOI/IOE
S	Z	L/V	C	F	R	SP	S	D
-	-	-	-

Description

A signed multiplication operation is performed on the 16-bit binary integers in the BC and DE registers. The signed 32-bit result is loaded in HL (bits 31 through 16) and BC (bits 15 through 0) registers.

Examples:

LD BC, 0FFFFh    ;BC gets -1
LD DE, 0FFFFh    ;DE gets -1
MUL              ;HL|BC = 1, HL gets 0000h, BC gets 0001h

In the above example, the 2's complement of FFFFh is 0001h.

LD BC, 0FFFFh    ;BC gets -1
LD DE, 00001h    ;DE gets 1
MUL              ;HL|BC = -1, HL gets FFFFh, BC gets FFFFh