When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. The Port 1 output buffers can sink/sourceįour TTL inputs. Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Power Down Mode saves the RAM contents but freezes the oscillator disablingĪll other chip functions until the next hardware reset. Serial port and interrupt system to continue function-ing. External pullups are required during program verifica-tion. Port 0 also receives the code bytes during Flash program-ming, and outputs the code bytes during program verifica-tion.

The Idle Mode stops the CPU while allowing the RAM, timer/count-ers, In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. In this mode P0 has internal pul-lups.ĭuplex serial port, on-chip oscillator and clock circuitry. Port 0 may also be configured to be the multiplexed low-order address/data bus during accesses to external pro-gram and data memory. Pins can be used as high-im-pedance inputs. The AT89C51 provides the following standard features: 4 Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architec-ture, a full As an output port each pin can sink eight TTL inputs. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51 The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4 Kbytes of Flash Programmable and Erasable Read Only Memory (PEROM). Microcomputer which provides a highly flexible and 4 Kbytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase CyclesĬost effective solution to many embedded controlĪpplications.

Monolithic chip, the Atmel AT89C51 is a powerful

Atmel 89c51 datasheet