HCS12 datasheet(71/452 Pages) FREESCALE

部件名	HCS12

功能描述	HCS12 Microcontrollers

PDF	452 Pages

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制造商	FREESCALE [Freescale Semiconductor, Inc]

网页	http://www.freescale.com

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71 / 452 page

S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

5.17 Multiply and Accumulate Instruction

The multiply and accumulate (EMACS) instruction multiplies two 16-bit

operands stored in memory and accumulates the 32-bit result in a third

memory location. EMACS can be used to implement simple digital filters

and defuzzification routines that use 16-bit operands. The WAV instruction

incorporates an 8- to 16-bit multiply and accumulate operation that obtains

a numerator for the weighted average calculation. The EMACS instruction

can automate this portion of the averaging operation when 16-bit operands

are used. Table 5-15 shows the EMACS instruction.

Table 5-15. Multiply and Accumulate Instructions

Mnemonic

Function

Operation

EMACS

Multiply and accumulate (signed)

16 bit by 16 bit

⇒ 32 bit

((M(X):M(X+1)) × (M(Y):M(Y+1)))

+ (M ~ M + 3)

⇒ M ~ M + 3

HCS12 数据表(PDF) 71 Page - Freescale Semiconductor, Inc