參數(shù)資料
型號： ENC624J600T-I/PT
廠商： Microchip Technology
文件頁數(shù)： 155/168頁
文件大小： 0K
描述： IC ETHERNET CTRLR W/SPI 64-TQFP
視頻文件： Fast 100 Mbps Ethernet PICtail Plus Overview
標準包裝： 1,200
控制器類型： 以太網(wǎng)控制器（IEEE 802.3）
接口： SPI
電源電壓： 3 V ~ 3.6 V
電流 - 電源： 96mA
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 64-TQFP
供應商設備封裝： 64-TQFP（10x10）
包裝： 帶卷 (TR)
配用： AC164132-ND - BOARD DAUGHTER PICTAIL ETHERNET
2007 Microchip Technology Inc.
DS39599G-page 85
PIC18F2220/2320/4220/4320
8.0
8 X 8 HARDWARE MULTIPLIER
8.1
Introduction
An 8 x 8 hardware multiplier is included in the ALU of
the PIC18F2X20/4X20 devices. By making the multiply
a hardware operation, it completes in a single instruc-
tion cycle. This is an unsigned multiply that gives a
16-bit result. The result is stored into the 16-bit product
register pair (PRODH:PRODL). The multiplier does not
affect any flags in the STATUS register.
Making the 8 x 8 multiplier execute in a single-cycle
gives the following advantages:
Higher computational throughput
Reduces code size requirements for multiply
algorithms
The performance increase allows the device to be used
in applications previously reserved for Digital Signal
Processors.
Table 8-1 shows a performance comparison between
enhanced devices using the single-cycle hardware
multiply and performing the same function without the
hardware multiply.
8.2
Operation
Example 8-1 shows the sequence to do an 8 x 8
unsigned multiply. Only one instruction is required
when one argument of the multiply is already loaded in
the WREG register.
Example 8-2 shows the sequence to do an 8 x 8 signed
multiply. 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
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
@ 40 MHz
@ 10 MHz
@ 4 MHz
8 x 8 unsigned
Without hardware multiply
13
69
6.9
μs
27.6
μs
69
μs
Hardware multiply
1
100 ns
400 ns
1
μs
8 x 8 signed
Without hardware multiply
33
91
9.1
μs
36.4
μs
91
μs
Hardware multiply
6
600 ns
2.4
μs6 μs
16 x 16 unsigned
Without hardware multiply
21
242
24.2
μs
96.8
μs242 μs
Hardware multiply
28
2.8
μs11.2 μs28 μs
16 x 16 signed
Without hardware multiply
52
254
25.4
μs102.6 μs254 μs
Hardware multiply
35
40
4.0
μs
16.0
μs
40
μs
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