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1、Features Compatible with MCS 51Products 2K Bytes of Reprogrammable Flash Memory Endurance 10 000 Write Erase Cycles 2 7V to 6V Operating Range Fully Static Operation 0 Hz to 24 MHz Two level Program Memory Lock 128 x 8 bit Internal RAM 15 Programmable I O Lines Two 16 bit Timer Counters Six Interrup
2、t Sources Programmable Serial UART Channel Direct LED Drive Outputs On chip Analog Comparator Low power Idle and Power down Modes Green Pb Halide free Packaging Option 1 Description The AT89C2051 is a low voltage high performance CMOS 8 bit microcomputer with 2K bytes of Flash programmable and erasa
3、ble read only memory PEROM The device is manufactured using Atmel s high density nonvolatile memory technology and is compatible with the industry standard MCS 51 instruction set By combining a versatile 8 bit CPU with Flash on a monolithic chip the Atmel AT89C2051 is a power ful microcomputer which
4、 provides a highly flexible and cost effective solution to many embedded control applications The AT89C2051 provides the following standard features 2K bytes of Flash 128 bytes of RAM 15 I O lines two 16 bit timer counters a five vector two level interrupt architecture a full duplex serial port a pr
5、ecision analog comparator on chip oscillator and clock circuitry In addition the AT89C2051 is designed with static logic for opera tion down to zero frequency and supports two software selectable power saving modes The Idle Mode stops the CPU while allowing the RAM timer counters serial port and int
6、errupt 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 8 bit Microcontroller with 2K Bytes Flash AT89C2051 0368H MICRO 6 08 2 0368H MICRO 6 08 AT89C2051 2 Pin Configuration 2 120 lea
7、d PDIP SOIC 3 Block Diagram 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 RST VPP RXD P3 0 TXD P3 1 XTAL2 XTAL1 INT0 P3 2 INT1 P3 3 TO P3 4 T1 P3 5 GND VCC P1 7 P1 6 P1 5 P1 4 P1 3 P1 2 P1 1 AIN1 P1 0 AIN0 P3 7 3 0368H MICRO 6 08 AT89C2051 4 Pin Description 4 1VCC Supply voltage 4 2GND Ground 4
8、 3Port 1 The Port 1 is an 8 bit bi directional I O port Port pins P1 2 to P1 7 provide internal pull ups P1 0 and P1 1 require external pull ups P1 0 and P1 1 also serve as the positive input AIN0 and the negative input AIN1 respectively of the on chip precision analog comparator The Port 1 out put
9、buffers can sink 20 mA and can drive LED displays directly When 1s are written to Port 1 pins they can be used as inputs When pins P1 2 to P1 7 are used as inputs and are externally pulled low they will source current IIL because of the internal pull ups Port 1 also receives code data during Flash p
10、rogramming and verification 4 4Port 3 Port 3 pins P3 0 to P3 5 P3 7 are seven bi directional I O pins with internal pull ups P3 6 is hard wired as an input to the output of the on chip comparator and is not accessible as a gen eral purpose I O pin The Port 3 output buffers can sink 20 mA When 1s are
11、 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 AT89C2051 as listed below Por
12、t 3 also receives some control signals for Flash programming and verification 4 5RST Reset input All I O pins are reset to 1s as soon as RST goes high Holding the RST pin high for two machine cycles while the oscillator is running resets the device Each machine cycle takes 12 oscillator or clock cyc
13、les 4 6XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit Port PinAlternate Functions P3 0RXD serial input port P3 1TXD serial output port P3 2INT0 external interrupt 0 P3 3INT1 external interrupt 1 P3 4T0 timer 0 external input P3 5T1 timer 1 externa
14、l input 4 0368H MICRO 6 08 AT89C2051 4 7XTAL2 Output from the inverting oscillator amplifier 5 Oscillator Characteristics The XTAL1 and XTAL2 are the input and output respectively of an inverting amplifier which can be configured for use as an on chip oscillator as shown in Figure 5 1 Either a quart
15、z crystal or ceramic resonator may be used To drive the device from an external clock source XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 5 2 There are no require ments on the duty cycle of the external clock signal since the input to the internal clocking circuitry is t
16、hrough a divide by two flip flop but minimum and maximum voltage high and low time specifications must be observed Figure 5 1 Oscillator Connections Note C1 C2 30 pF 10 pF for Crystals 40 pF 10 pF for Ceramic Resonators Figure 5 2 External Clock Drive Configuration 5 0368H MICRO 6 08 AT89C2051 6 Special Function Registers A map of the on chip memory area called the Special Function Register SFR space is shown in the table below Note that not all of the addresses are occupied and unoccupied addre
