参数资料
型号: AT89LP51-20PU
厂商: Atmel
文件页数: 44/117页
文件大小: 0K
描述: MCU 8051 4K FLASH 20MHZ
标准包装: 10
系列: 89LP
核心处理器: 8051
芯体尺寸: 8-位
速度: 20MHz
连通性: EBI/EMI,I²C,SPI,UART/USART
外围设备: 欠压检测/复位,POR,PWM,WDT
输入/输出数: 36
程序存储器容量: 4KB(4K x 8)
程序存储器类型: 闪存
RAM 容量: 256 x 8
电压 - 电源 (Vcc/Vdd): 2.4 V ~ 5.5 V
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 40-DIP(0.600",15.24mm)
包装: 管件
32
3709D–MICRO–12/11
AT89LP51/52
7.
Reset
During reset, all I/O Registers are set to their initial values, the port pins are set to their default
mode, and the program starts execution from the Reset Vector, 0000H. The AT89LP51/52 has
five sources of reset: power-on reset, brown-out reset, external reset, watchdog reset, and soft-
ware reset.
7.1
Power-on Reset
A Power-on Reset (POR) is generated by an on-chip detection circuit. The detection level V
POR
is nominally 1.4V. The POR is activated whenever V
DD is below the detection level. The POR cir-
cuit can be used to trigger the start-up reset or to detect a major supply voltage failure. The POR
circuit ensures that the device is reset from power-on. A power-on sequence is shown in Figure
7-1. When V
DD reaches the Power-on Reset threshold voltage VPOR, an initialization sequence
lasting t
POR is started. When the initialization sequence completes, the start-up timer determines
how long the device is kept in POR after V
DD rise. The start-up timer does not begin counting
until after V
DD reaches the Brown-out Detector (BOD) threshold voltage VBOD. The POR signal is
activated again, without any delay, when V
DD falls below the POR threshold level. A Power-on
Reset (i.e. a cold reset) will set the POF flag in PCON. The internally generated reset can be
extended beyond the power-on period by holding the RST pin active longer than the time-out.
Figure 7-1.
Power-on Reset Sequence
Note:
t
POR is approximately 143 s ± 5%.
The start-up timer delay is user-configurable with the Start-up Time User Fuses and depends on
the clock source (Table 7-1). The Start-Up Time fuses also control the length of the start-up time
after a Brown-out Reset or when waking up from Power-down during internally timed mode. The
start-up delay should be selected to provide enough settling time for V
DD and the selected clock
source. The device operating environment (supply voltage, frequency, temperature, etc.) must
meet the minimum system requirements before the device exits reset and starts normal opera-
tion. The RST pin may be held active externally until these conditions are met.
VDD
RST
Time-out
t
POR
t
RHD
V
POR
Internal
Reset
RST
Internal
Reset
V
IL
t
SUT
V
BOD
(RST Tied to GND)
(RST Controlled Externally)
POL
(POL Tied to VCC)
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