ATMEL AT89S52 is a 8051/52 compatible 8 bit microcontroller, comes in 40 Pin DIP package. It has 8K bytes of In-System Programmable (ISP) Flash memory.
The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes
of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a
six-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 interrupt
or hardware reset.