AT89C2051 Features:
- 2K bytes of Reprogrammable Flash Memory (PEROM) - Endurance: 1,000 Write/Erase Cycles
- 2.7V to 6V operating range
- 128 x 8 bytes of RAM
- 15 Programmable I/O lines (Ports 1.0-1.7 & Ports 3.0-3.5 & 3.7)
Pin Configuration:
- VCC (Pin 20) – Supply Voltage
- GND (Pin 10) – GroundPort 1 (Pins 12 – 19) – 8 Bit bi-directional I/O port
- Port 3 (Pins 2-3,6-9, 11) - Seven bi-directional I/O pins with internal pull-ups
- RST (Pin 1) - Reset input
- XTAL1 (Pin 5) - Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
- XTAL2 (Pin 4) - Output from the inverting oscillator amplifier.
- 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)
- P3.6 is hard-wired as an input to the output of the on-chip comparator and is not accessible as a general-purpose I/O pin.
Block Diagram:
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
Note: C1, C2 = 10-30 pF ± 10 pF for Crystals
