【正文】 d insystem or by a conventional nonvolatile memory programmer. By bining a versatile 8bit CPU with Flash on a monolithic chip, the Atmel STC89C52 is a powerful microputer which provides a highly flexible and cost effective solution to many embedded control applications.STC89C52 has the following features: 40pin, 4k Bytes Flash chip program memory, 128 bytes of random access data memory (RAM), 32 external bidirectional input / output (I / O) ports, interrupt priority level 2 5 Interrupt nesting level interrupts, two 16bit programmable timer counters, two full duplex serial port, watchdog (WDT) circuit, the onchip clock oscillator. In addition, STC89C52 design and configuration of the oscillation frequency can be set to 0Hz and through the software powersaving mode. Idle mode, CPU to suspend work, and RAM timing counters, serial port, and interrupt system to continue, but freezes the oscillator powerdown mode save RAM, disabling all other chip functions until the next interrupt or hardware reset. Meanwhile, the chip also has PDIP, TQFP and PLCC packages such as three, to acmodate different productsFeatures OverviewThe STC89C52 provides the following standard features: 4K bytes of Flash,128 bytes of RAM, 32 I/O lines, two 16bit timer/counters, a five vector twolevel interrupt architecture, a full duplex serial port, onchip oscillator and clock circuitry. In addition, the STC89C52 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, timer/counters, serial port and interrupt system to continue functioning. The Powerdown Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Features? Compatible with MCS51? Products? 4K Bytes of InSystem Reprogrammable Flash Memory– Endurance: 1,000 Write/Erase Cycles? Fully Static Operation: 0 Hz to 24 MHz? ThreeLevel Program Memory Lock? 128 x 8Bit Internal RAM? 32 Programmable I/O Lines? Two 16Bit Timer/Counters? Six Interrupt Sources? Programmable Serial Channel? Low Power Idle and Power Down ModesPin Function Description:VCC：Supply voltage.GND：Ground.Port 0Port 0 is an 8bit opendrain bidirectional I/O 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 highimpedance inputs. Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pullups are required during program verification. Port 1Port 1 is an 8bit bidirectional I/O port with internal Port 1 output buffers can sink/source four TTL 1s are written to Port 1 pins they are pulled high by the internal pullups 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 1 also receives the loworder address bytes during Flash programming and verification. Port 2Port 2 is an 8bit bidirectional I/O port with internal Port 2 output buffers can sink/source four TTL 1s are written to Port 2 pins they are pulled high by the internal pullups 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 pullups. Port 2 emits the highorder address byte during fetches from external program memory and during accesses to external data memory that use 16bit addresses (MOVX @DPTR). In this application, it uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the highorder address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8bit bidirectional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special features of the STC89C52 as listed below:Port 3 also receives some control signals for Flash programming and verification. RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device. ALE/PROGAddress 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 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external DataMemory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALEdisable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to , however, that if lock bit 1