PIC18F4682T-I/ML【PDF 17/183 页】IC PIC MCU FLASH 40KX16 44QFN

收藏本站

您好，
买卖IC网欢迎您。
请登录
免费注册

买卖IC网

Sheet目录3871

13页 14页 15页 16页 [17页]18页 19页 20页 21页

2011 Microchip Technology Inc.

DS39931D-page 113

PIC18F46J50 FAMILY

8.0

8 x 8 HARDWARE MULTIPLIER

8.1

Introduction

All PIC18 devices include an 8 x 8 hardware multiplier

as part of the ALU. The multiplier performs an unsigned

operation and yields a 16-bit result that is stored in the

product register pair, PRODH:PRODL. The multiplier’s

operation does not affect any flags in the STATUS

Making multiplication a hardware operation allows it to

be completed in a single instruction cycle. This has the

advantages of higher computational throughput and

reduced code size for multiplication algorithms and

allows the PIC18 devices to be used in many applica-

tions previously reserved for digital signal processors.

Table 8-1 provides a comparison of various hardware

and software multiply operations, along with the

savings in memory and execution time.

8.2

Operation

Example 8-1 provides the instruction sequence for an

8 x 8 unsigned multiplication. Only one instruction is

required when one of the arguments is already loaded

in the WREG register.

Example 8-2 provides the instruction sequence for an

8 x 8 signed multiplication. To account for the sign bits

of the arguments, each argument’s Most Significant bit

(MSb) is tested and the appropriate subtractions are

done.

EXAMPLE 8-1:

8 x 8 UNSIGNED MULTIPLY

ROUTINE

EXAMPLE 8-2:

8 x 8 SIGNED MULTIPLY

ROUTINE

TABLE 8-1:

PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS

MOVF

ARG1, W

;

MULWF

ARG2

; ARG1 * ARG2 ->

; PRODH:PRODL

MOVF

ARG1, W

MULWF

ARG2

; ARG1 * ARG2 ->

; PRODH:PRODL

BTFSC

ARG2, SB

; Test Sign Bit

SUBWF

PRODH, F

; PRODH = PRODH

;

- ARG1

MOVF

ARG2, W

BTFSC

ARG1, SB

; Test Sign Bit

SUBWF

PRODH, F

; PRODH = PRODH

;

- ARG2

Routine

Multiply Method

Program

Memory

(Words)

Cycles

(Max)

Time

@ 48 MHz

@ 10 MHz

@ 4 MHz

8 x 8 unsigned

Without hardware multiply

5.7

s27.6 s69 s

Hardware multiply

83.3 ns

400 ns

8 x 8 signed

Without hardware multiply

7.5

s36.4 s91 s

Hardware multiply

500 ns

2.4

s6 s

16 x 16 unsigned

Without hardware multiply

242

20.1

s96.8 s242 s

Hardware multiply

2.3

11.2

s28 s

16 x 16 signed

Without hardware multiply

254

21.6

102.6

s254 s

Hardware multiply

3.3

s16.0 s40 s

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

采购需求

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

我的联系方式