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基于51单片机的电子数字钟设计的外文翻译
AT89C51 Family Users Guide 1 Features
Compatible with MCS-51 Products
4K Bytes of In-System Reprogrammable Flash Memory – Endurance 1000 WriteErase Cycles Fully Static Operation 0 Hz to 24 MHz Three-level Program Memory Lock 128 x 8-bit Internal RAM 32 Programmable IO Lines Two 16-bit TimerCounters Six Interrupt Sources Programmable Serial Channel
Low-power Idle and Power-down Modes 2 Description
The AT89C51 is a low-power high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory PEROM The device is manufactured using Atmels high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pin-out The on-chip Flash allows the program memory
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to be reprogrammed in-system or by a conventional nonvolatile memory programmer By combining a versatile 8-bit CPU with Flash on a monolithic chip the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications
3 Pin Configurations
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4 Lock Diagram
The AT89C51 provides the following standard features 4K bytes of Flash 128 bytes of RAM 32 IO lines two 16-bit timercounters a five vector two-level interrupt architecture a full duplex serial port on-chip oscillator and clock circuitry In addition the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes The Idle Mode stops the CPU while allowing the RAM timercounters serial port and interrupt system to continue functioning The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset
5 Pin Description VCC Supply voltage GND Ground Port 0
Port 0 is an 8-bit open-drain bi-directional IO port As an output port each pin can sink eight TTL inputs When 1s are written to port 0 pins the pins can be used as high-impedance inputs
Port 0 may also be configured to be the multiplexed low-order addressdata bus during accesses to external program and data memory In this mode P0 has internal pull-ups
Port 0 also receives the code bytes during Flash programming and
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outputs the code bytes during program verification External pull-ups are required during program verification
Port 1
Port 1 is an 8-bit bi-directional IO port with internal pull-ups The Port 1 output buffers can sinksource four TTL inputs When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs As inputs Port 1 pins that are externally being pulled low will source current IIL because of the internal pull-ups Port 1 also receives the low-order address bytes during Flash programming and verification
Port 2
Port 2 is an 8-bit bi-directional IO port with internal pull-ups The Port 2 output buffers can sinksource four TTL inputs When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs As inputs Port 2 pins that are externally being pulled low will source current IIL because of the internal pull-ups Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses MOVX DPTR In this application it uses strong internal pull-ups when emitting 1s During accesses to external data memory that uses 8-bit addresses MOVX RI Port 2 emits the contents of the P2 Special Function Register Port 2 also receives the high-order address bits and some control
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signals during Flash programming and verification
Port 3
Port 3 is an 8-bit bi-directional IO port with internal pull-ups The Port 3 output buffers can sinksource four TTL inputs When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs As inputs Port 3 pins that are externally being pulled low will source current IIL because of the pull-ups Port 3 also serves the functions of various special features of the AT89C51 as listed below
Port Pin Alternate Functions
P31 TXD serial output port
P30 RXD serial input port
P32 INT0 external interrupt 0
P34 T0 timer 0 external input P36 WR external data memory write
Port
3
P33 INT1 external interrupt 1 P35 T1 timer 1 external input
strobe P37 RD external data memory read strobe
also receives some control signals for Flash programming and verification
RST
Reset input A high on this pin for two machine cycles while the oscillator is running resets the device
ALE
Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory This pin is also the program pulse input PROG during Flash programming In normal operation ALE is emitted at a constant rate of 16 the oscillator frequency and may be used
基于51单片机的电子数字钟设计的外文翻译
