i think you should just take a look at 89c51RD2 specs, some features are listed below:

Hope you will find this useful,

Vineet Kulkarni

The P89C51RB2/RC2/RD2 device contains a non-volatile
16kB/32kB/64kB Flash program memory that is both parallel
programmable and serial In-System and In-Application
Programmable. In-System Programming (ISP) allows the user to
download new code while the microcontroller sits in the application.
In-Application Programming (IAP) means that the microcontroller
fetches new program code and reprograms itself while in the
system. This allows for remote programming over a modem link.
A default serial loader (boot loader) program in ROM allows serial
In-System programming of the Flash memory via the UART without
the need for a loader in the Flash code. For In-Application
Programming, the user program erases and reprograms the Flash
memory by use of standard routines contained in ROM.
This device executes one machine cycle in 6 clock cycles, hence
providing twice the speed of a conventional 80C51. An OTP
configuration bit lets the user select conventional 12 clock timing
if desired.
This device is a Single-Chip 8-Bit Microcontroller manufactured in
advanced CMOS process and is a derivative of the 80C51
microcontroller family. The instruction set is 100% compatible with
the 80C51 instruction set.
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The device also has four 8-bit I/O ports, three 16-bit timer/event
counters, a multi-source, four-priority-level, nested interrupt structure,
an enhanced UART and on-chip oscillator and timing circuits.
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The added features of the P89C51RB2/RC2/RD2 makes it a
powerful microcontroller for applications that require pulse width
modulation, high-speed I/O and up/down counting capabilities such
as motor control.
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• 80C51 Central Processing Unit
• On-chip Flash Program Memory with In-System Programming
(ISP) and In-Application Programming (IAP) capability
• Boot ROM contains low level Flash programming routines for
downloading via the UART
• Can be programmed by the end-user application (IAP)
• 6 clocks per machine cycle operation (standard)
• 12 clocks per machine cycle operation (optional)
• Speed up to 20 MHz with 6 clock cycles per machine cycle
(40 MHz equivalent performance); up to 33 MHz with 12 clocks
per machine cycle
• Fully static operation
• RAM expandable externally to 64 kB
• 4 level priority interrupt
• 7 interrupt sources
• Four 8-bit I/O ports
• Full-duplex enhanced UART
– Framing error detection
– Automatic address recognition
• Power control modes
– Clock can be stopped and resumed
– Idle mode
– Power down mode
• Programmable clock out
• Second DPTR register
• Asynchronous port reset
• Low EMI (inhibit ALE)
• Programmable Counter Array (PCA)
– PWM
– Capture/compare