W79E825A/824A/823B/822B Data Sheet
6
FUNCTIONAL DESCRIPTION
The W79E825 series architecture consist of a 4T 8051 core controller surrounded by various registers,
16K/8K/4K/2K bytes Flash EPROM, 256/128 bytes of RAM, 256/128 bytes NVM Data Flash EPROM,
three general purpose I/O ports, two timer/counters, one serial port, one I2C serial I/O, 4 channel
PWM with 10-bit counter, 4-channel multiplexed with 10-bit ADC analog input, Flash EPROM program
by Writer and ICP.
6.1 On-Chip Flash EPROM
The W79E825 series include one 16K/8K/4K/2K bytes of main Flash EPROM for application program.
A Writer or ICP programming board is required to program the Flash EPROM or NVM Data Flash
EPROM.
This ICP (In-Circuit Programming) feature makes the job easy and efficient when the application’s
firmware needs to be updated frequently. In some applications, the in-circuit programming feature
makes it possible for the end-user to easily update the system firmware without opening the chassis.
6.2 I/O Ports
The W79E825 series have two 8-bit and one 2-bit port, up to 18 I/O pins using on-chip oscillator &
/RST is input only by reset options. All ports can be used as four outputs mode when it may set by
PxM1.y and PxM2.y SFR’s registers, it has strong pull-ups and pull-downs, and does not need any
external pull-ups. Otherwise it can be used as general I/O port as open drain circuit. All ports can be
used bi-directional and these are as I/O ports. These ports are not true I/O, but rather are pseudo-I/O
ports. This is because these ports have strong pull-downs and weak pull-ups.
6.3 Serial I/O
The W79E825 series have one serial port that is functionally similar to the serial port of the original
8032 family. However the serial port on the W79E825 series 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.
6.4 Timers
The W79E825 series have two 16-bit timers that are functionally and similar to the timers of the 8052
family. When used as timers, the user has a choice of 12 or 4 clocks per count that emulates the
timing of the original 8052.
6.5 Interrupts
The Interrupt structure in the W79E825 series is slightly different from that of the standard 8052. Due
to the presence of additional features and peripherals, the number of interrupt sources and vectors
has been increased.
6.6 Data Pointers
The data pointers of W79E825 series are same as 8052 that has dual 16-bit Data Pointers (DPTR) by
setting DPS bit at AUXR1.0. The figure of dual DPTR is as below diagram.
Publication Release Date: February 21, 2008
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Revision A9
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