First step to proceed with Reverse Engineering W78E52B Chip Data is to understand its main features and general description:

The W78E51B is an 8-bit microcontroller which can accommodate a wider frequency range with low power consumption. The instruction set for the W78E52B is fully compatible with the standard 8051. The W78E52B contains an 4K bytes Flash EPROM; a 128 bytes RAM; four 8-bit bi-directional and bit- addressable I/O ports; an additional 4-bit I/O port P4; two 16-bit timer/counters; a hardware watchdog timer and a serial port. These peripherals are supported by seven sources two-level interrupt capability. To facilitate programming and verification, the Flash EPROM inside the W78E52B allows the program memory to be programmed and read electronically. Once the code is confirmed, the user can protect the code for security.
The W78E51B microcontroller has two power reduction modes, idle mode and power-down mode, both of which are software selectable. The idle mode turns off the processor clock but allows for continued peripheral operation. The power-down mode stops the crystal oscillator for minimum power consumption. The external clock can be stopped at any time and in any state without affecting the processor.

Fully static design 8-bit CMOS microcontroller
Wide supply voltage of 4.5V to 5.5V
128 bytes of on-chip scratchpad RAM
4 KB On-chip Flash EPROM
64 KB program memory address space
64 KB data memory address space
Four 8-bit bi-directional ports

One extra 4-bit bit-addressable I/O port, additional INT2 / INT3 (available on 44-pin PLCC/QFP package)
Two 16-bit timer/counters
One full duplex serial port(UART)
Watchdog Timer
Seven sources, two-level interrupt capability
EMI reduction mode
Built-in power management
Code protection mechanism

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