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| 型號： | AT89C55WD-24PU |
| 廠商： | Atmel |
| 文件頁數(shù)： | 27/34頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC 8051 MCU FLASH 20K 40DIP |
| 產(chǎn)品培訓(xùn)模塊： | MCU Product Line Introduction |
| 標(biāo)準(zhǔn)包裝： | 10 |
| 系列： | 89C |
| 核心處理器： | 8051 |
| 芯體尺寸： | 8-位 |
| 速度： | 24MHz |
| 連通性： | UART/USART |
| 外圍設(shè)備： | WDT |
| 輸入/輸出數(shù)： | 32 |
| 程序存儲器容量： | 20KB（20K x 8） |
| 程序存儲器類型： | 閃存 |
| RAM 容量： | 256 x 8 |
| 電壓 - 電源 (Vcc/Vdd)： | 4.5 V ~ 5.5 V |
| 振蕩器型： | 內(nèi)部 |
| 工作溫度： | -40°C ~ 85°C |
| 封裝/外殼： | 40-DIP（0.600"，15.24mm） |
| 包裝： | 管件 |
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2007 Microchip Technology Inc.
DS41239D-page 31
PIC10F200/202/204/206
6.1.2
TIMER0 INCREMENT DELAY
Since the prescaler output is synchronized with the
internal clocks, there is a small delay from the time the
external clock edge occurs to the time the Timer0
module is actually incremented. Figure 6-4 shows the
delay from the external clock edge to the timer
incrementing.
FIGURE 6-4:
TIMER0 TIMING WITH EXTERNAL CLOCK
6.2
Prescaler
An 8-bit counter is available as a prescaler for the
Timer0 module or as a postscaler for the Watchdog
Timer (WDT), respectively (see Section 9.6 “Watch-
dog Timer (WDT)”). For simplicity, this counter is
being referred to as “prescaler” throughout this data
sheet.
The PSA and PS<2:0> bits (OPTION<3:0>) determine
prescaler assignment and prescale ratio.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g., CLRF 1, MOVWF 1,
BSF 1,x, etc.) will clear the prescaler. When assigned
to WDT, a CLRWDT instruction will clear the prescaler
along with the WDT. The prescaler is neither readable
nor writable. On a Reset, the prescaler contains all ‘0’s.
6.2.1
SWITCHING PRESCALER
ASSIGNMENT
The prescaler assignment is fully under software
control (i.e., it can be changed “on-the-fly” during pro-
gram execution). To avoid an unintended device Reset,
the following instruction sequence (Example 6-1) must
be executed when changing the prescaler assignment
from Timer0 to the WDT.
EXAMPLE 6-1:
CHANGING PRESCALER
(TIMER0
→ WDT)
Increment Timer0 (Q4)
External Clock Input or
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Timer0
T0
T0 + 1
T0 + 2
Small pulse
misses sampling
External Clock/Prescaler
Output After Sampling
(3)
Prescaler Output(2)
(1)
Note 1: Delay from clock input change to Timer0 increment is 3 TOSC to 7 TOSC (Duration of Q = TOSC). Therefore, the error
in measuring the interval between two edges on Timer0 input = ±4 TOSC max.
2: External clock if no prescaler selected; prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
Note:
The prescaler may be used by either the
Timer0 module or the WDT, but not both.
Thus, a prescaler assignment for the
Timer0 module means that there is no
prescaler for the WDT and vice versa.
CLRWDT
;Clear WDT
CLRF
TMR0
;Clear TMR0 & Prescaler
MOVLW
‘00xx1111’b ;These 3 lines (5, 6, 7)
OPTION
;are required only if
;desired
CLRWDT
;PS<2:0> are 000 or 001
MOVLW
‘00xx1xxx’b ;Set Postscaler to
OPTION
;desired WDT rate
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| AT89C55WD-24PU SL383 | 制造商:Atmel Corporation 功能描述:8051 MCU 20K FLASH 4.0 TO 5.5V |
| AT89C55WD-33AC | 功能描述:8位微控制器 -MCU Microcontroller RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| AT89C55WD-33AU | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:8-bit Microcontroller with 20K Bytes Flash |
| AT89C55WD-33JC | 功能描述:8位微控制器 -MCU Microcontroller RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| AT89C55WD-33JI | 功能描述:8位微控制器 -MCU 80C31 w/20k RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
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