《单片机外文文献英文文献外文翻译AT89系列单片机》由会员分享，可在线阅读，更多相关《单片机外文文献英文文献外文翻译AT89系列单片机（10页珍藏版）》请在金锄头文库上搜索。
1、The series SCM of AT89 1.1 AT89C511.Featuresl 4K Bytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cyclesl Three-level Program Memory Lockl 128 x 8-bit Internal RAMl 32 Programmable I/O Linesl Two 16-bit Timer/Countersl Six Interrupt Sourcesl Low-power Idle and Power-down M
2、odes2.DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes 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 inst
3、ruction set and pinout. The on-chip Flash allows the program memory 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
4、cost-effective.3.Pin Configurations4Pin DescriptionVCCSupply voltage.GNDGround.Figure A1Port 0Port 0 is an 8-bit open-drain bi-directional 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 high-impedance inputs. Port 0 may al
5、so be configured to be the multiplexed low-order 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 requ
6、ired during program verification.Port 1Port 1 is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output buffers can sink/source four TTL inputs. When 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 a
7、re externally being pulled low will source current (TTL) because of the internal pullups. Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups. The Port 2 output buffers can sink/source four
8、TTL inputs. When 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 (TTL) because of the internal pullups. Port 2 emits the high-order address byte during fetches from e
9、xternal program memory and during accesses to external data memory that use 16-bit addresses (MOVX DPTR). In this application, it uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX RI), Port 2 emits the contents of the P2 Special Fun
10、ction Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins th
11、ey 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 (TTL) because of the pullups. Port 3 also serves the functions of various special features of the AT89C51 as listed below:Port 3 also receives some co
12、ntrol signals for Flash programming and verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the devicePSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSE
13、N is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.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) duri
14、ng 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 Data Memory. If desired, ALE operation can be disabled by
15、 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 ALE-disable bit has no effect if the microcontroller is in external execution mode.EA/VPPExternal Access Enable. EA must be strapped to GN
16、D in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to th
