W79E201 Datasheet, PDF (7/87 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E201
6. FUNCTIONAL DESCRIPTION
The W79E201 is not pin compatible with 8052 but the instruction set is compatible. It includes the
resources of the standard 8052 such as three 8-bit I/O Ports, one 8-bit digital or analog input port,
three 16-bit timer/counters, one full duplex serial port and interrupt sources.
The W79E201 features a faster running and better performance 8-bit CPU with a redesigned core
processor without wasted clock and memory cycles. it improves the performance not just by running
at high frequency but also by reducing the machine cycle duration from the standard 8052 period of
twelve clocks to four clock cycles for the majority of instructions. This improves performance by an
average of 1.5 to 3 times. It can also adjust the duration of the MOVX instruction (access to off-chip
data memory) between two machine cycles and nine machine cycles. This flexibility allows the
W79E201 to work efficiently with both fast and slow RAMs and peripheral devices.
The W79E201 is an 8052 compatible device that gives the user the features of the original 8052
device, but with improved speed and power consumption characteristics. It has the same instruction
set as the 8051 family. While the original 8051 family was designed to operate at 12 clock periods per
machine cycle, the W79E201 operates at a much reduced clock rate of only 4 clock periods per
machine cycle. This naturally speeds up the execution of instructions. Consequently, the W79E201
can run at a higher speed as compared to the original 8052, even if the same crystal is used. Since
the W79E201 is a fully static CMOS design, it can also be operated at a lower crystal clock, giving the
same throughput in terms of instruction execution, yet reducing the power consumption.
The 4 clocks per machine cycle feature in the W79E201 is responsible for a three-fold increase in
execution speed. The W79E201 has all the standard features of the 8052, and has a few extra
peripherals and features as well.
I/O Ports
The W79E201 has one 8-bit digital or analog input port, Three 8-bit I/O ports and one extra 1-bit port
at P4.0. Port 0 can be used as an Address/Data bus when external program is running or external
memory/device is accessed by MOVC or MOVX instruction. In these cases, it has strong pull-ups and
pull-downs, and does not need any external pull-ups. Otherwise it can be used as a general I/O port
with open-drain circuit. Port 2 is used chiefly as the upper 8-bits of the Address bus when port 0 is
used as an address/data bus. It also has strong pull-ups and pull-downs when it serves as an address
bus. Port 1 is only input port which can be selected to 8-channel analog input pins of ADC. Port 3 act
as I/O ports with alternate functions. Port 4.0 serves as a general purpose I/O port as Port 3.
Serial I/O
The W79E201 has one enhanced serial port that is functionally similar to the serial port of the original
8052 family. However the serial port on the W79E201 can operate in different modes in order to obtain
timing similarity as well. The serial port has the enhanced features of Automatic Address recognition
and Frame Error detection.
Timers
The W79E201 has three 16-bit timers that are functionally similar to the timers of the 8052 family.
When used as timers, they can be set to run at either 4 clocks or 12 clocks per count, thus providing
the user with the option of operating in a mode that emulates the timing of the original 8052. The
W79E201 has an additional feature, the watchdog timer. This timer is used as a System Monitor or as
a very long time period timer.
Publication Release Date: December 16, 2004
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Revision A2