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Description

The at89s52 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM) and 128 bytes RAM. The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51?

instruction set and pinout. The chip combines a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel at89s52 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.

Features:

? Compatible with MCS-51? Products

? 4K Bytes of In-System Reprogrammable Flash Memory ? Endurance: 1,000 Write/Erase Cycles ? Fully Static Operation: 0 Hz to 24 MHz ? Three-Level Program Memory Lock ? 128 x 8-Bit Internal RAM ? 32 Programmable I/O Lines ? Two 16-Bit Timer/Counters ? Six Interrupt Sources

? Programmable Serial Channel

? Low Power Idle and Power Down Modes

The at89s52 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level

interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the at89s52 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 Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset. Pin Description:

VCC Supply voltage. GND Ground. Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When is 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 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 1 Port 1 is an 8-bit bidirectional 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 are externally being pulled low will source current (IIL) because of the internal pullups. Port 1 also receives the low-order address bytes during Flash programming and verification. Port 2 Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers can sink/source four 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 (IIL) because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups 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 Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port 3 Port 3 is an 8-bit bidirectional 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 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 at89s52 as listed below: Port pin alternate functions P3.0 rxd (serial input port) Port 3 also P3.1 txd (serial output port) receives some P3.2 ^int0 (external interrupt0) control signals for P3.3 ^int1 (external interrupt1) Flash programming P3.4 t0 (timer0 external input) and verification. P3.5 t1 (timer1 external input) RST P3.6 ^WR (external data memory write Reset input. A strobe) high on this pin for P3.7 ^rd (external data memory read strobe) two machine cycles while the oscillator is running resets the device. ALE/PROG Address Latch Enable output pulse for latching the low byte of the address