參數(shù)資料
型號(hào): PIC18LF2450T-I/SO
廠商: Microchip Technology
文件頁數(shù): 128/143頁
文件大?。?/td> 0K
描述: IC PIC MCU FLASH 8KX16 28SOIC
標(biāo)準(zhǔn)包裝: 1,600
系列: PIC® 18F
核心處理器: PIC
芯體尺寸: 8-位
速度: 48MHz
連通性: UART/USART,USB
外圍設(shè)備: 欠壓檢測(cè)/復(fù)位,HLVD,POR,PWM,WDT
輸入/輸出數(shù): 23
程序存儲(chǔ)器容量: 16KB(8K x 16)
程序存儲(chǔ)器類型: 閃存
RAM 容量: 768 x 8
電壓 - 電源 (Vcc/Vdd): 2 V ~ 5.5 V
數(shù)據(jù)轉(zhuǎn)換器: A/D 10x10b
振蕩器型: 內(nèi)部
工作溫度: -40°C ~ 85°C
封裝/外殼: 28-SOIC(0.295",7.50mm 寬)
包裝: 帶卷 (TR)
PIC18F2450/4450
2006 Microchip Technology Inc.
Advance Information
DS39760A-page 83
7.0
8 x 8 HARDWARE MULTIPLIER
7.1
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
register.
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.
A comparison of various hardware and software
multiply operations, along with the savings in memory
and execution time, is shown in Table 7-1.
7.2
Operation
Example 7-1 shows 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 7-2 shows the sequence to do 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 7-1:
8 x 8 UNSIGNED
MULTIPLY ROUTINE
EXAMPLE 7-2:
8 x 8 SIGNED MULTIPLY
ROUTINE
TABLE 7-1:
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
@ 40 MHz
@ 10 MHz
@ 4 MHz
8 x 8 unsigned
Without hardware multiply
13
69
6.9
μs27.6 μs69 μs
Hardware multiply
1
100 ns
400 ns
1
μs
8 x 8 signed
Without hardware multiply
33
91
9.1
μs36.4 μs91 μs
Hardware multiply
6
600 ns
2.4
μs6 μs
16 x 16 unsigned
Without hardware multiply
21
242
24.2
μs96.8 μs
242
μs
Hardware multiply
28
2.8
μs
11.2
μs28 μs
16 x 16 signed
Without hardware multiply
52
254
25.4
μs
102.6
μs
254
μs
Hardware multiply
35
40
4.0
μs16.0 μs40 μs
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