When Attack Winbond W78E051A Protected Eeprom, we need to have some general idea about its architecture. The W78E051A architecture consists of a core controller surrounded by various registers, five general purpose I/O ports, 256 bytes of RAM, three timer/counters, and a serial port. The processor supports 111 different opcodes and references both a 64K program address space and a 64K data storage space.
Timers 0, 1, and 2
Timers 0, 1, and 2 each consist of two 8-bit data registers. These are called TL0 and TH0 for Timer 0, TL1 and TH1 for Timer 1, and TL2 and TH2 for Timer 2. The TCON and TMOD registers provide control functions for timers 0 and 1. The T2CON register provides control functions for Timer 2. RCAP2H and RCAP2L are used as reload/capture registers for Timer 2.
The operations of Timer 0 and Timer 1 are the same as in the W78E051A. Timer 2 is a special feature of the W78E051A: it is a 16-bit timer/counter that is configured and controlled by the T2CON register. Like Timers 0 and 1, Timer 2 can operate as either an external event counter or as an internal timer after Attack Winbond W78E051A Protected Eeprom, depending on the setting of bit C/T2 in T2CON. Timer 2 has three operating modes: capture, auto- reload, and baud rate generator. The clock speed at capture or auto-reload mode is the same as that of Timers 0 and 1.
New Defined Peripheral
In order to be more suitable for I/O, an extra 4-bit bit-addressable port P4 and two external interrupt INT2 , INT3 has been added to either the PLCC or QFP 44-pin package. And description follows:
1. INT2 / INT3
Two additional external interrupts, INT2 and INT3 , whose functions are similar to those of external interrupt 0 and 1 in the standard 80C52. The functions/status of these interrupts are determined/shown by the bits in the XICON (External Interrupt Control) register. The XICON register is bit-addressable but is not a standard register in the standard 80C52. Its address is at 0C0H. To set/clear bits in the XICON register, one can use the “SETB (/CLR) bit” instruction. For example, “SETB 0C2H” sets the EX2 bit of XICON.