W79E548 Datasheet, PDF (8/79 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E548/W79L548
6. FUNCTIONAL DESCRIPTION
The W79E(L)548 is 8052 pin compatible and instruction set compatible. It includes the resources of
the standard 8052 such as four 8-bit I/O Ports, three 16-bit timer/counters, full duplex serial port and
interrupt sources.
The W79E(L)548 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
W79E(L)548 to work efficiently with both fast and slow RAMs and peripheral devices. In addition, the
W79E(L)548 contains on-chip 1KB MOVX SRAM, the address of which is between 0000H and
03FFH. It only can be accessed by MOVX instruction; this on-chip SRAM is optional under software
control.
The W79E(L)548 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 W79E(L)548 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 W79E(L)548
can run at a higher speed as compared to the original 8052, even if the same crystal is used. Since
the W79E(L)548 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 W79E(L)548 is responsible for a three-fold increase in
execution speed. The W79E(L)548 has all the standard features of the 8052, and has a few extra
peripherals and features as well.
I/O Ports
The W79E(L)548 has seven 8-bit ports and one extra 4-bit port. 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 and 3 act as I/O
ports with alternate functions. Port 4 serves as a general purpose I/O port as Port 1 and Port 3. Port5
~ Port7 are bi-directional I/O ports with internal pull resisters.
Serial I/O
The W79E(L)548 has one enhanced serial ports that are functionally similar to the serial port of the
original 8052 family. However the serial ports on the W79E(L)548 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.
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