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4289A–8051–09/03<br />
<strong>AT89C51ID2</strong><br />
Pulse Width Modulator Mode.............................................................................. 51<br />
PCA Watchdog Timer ......................................................................................... 52<br />
Serial I/O Port ...................................................................................... 53<br />
Framing Error Detection ..................................................................................... 53<br />
Automatic Address Recognition.......................................................................... 54<br />
Registers............................................................................................................. 56<br />
Baud Rate Selection for UART for Mode 1 and 3............................................... 56<br />
UART Registers.................................................................................................. 59<br />
Interrupt System ................................................................................. 64<br />
Registers............................................................................................................. 65<br />
Interrupt Sources and Vector Addresses............................................................ 72<br />
Power Management ............................................................................ 73<br />
Introduction ......................................................................................................... 73<br />
Idle Mode ............................................................................................................ 73<br />
Power-Down Mode ............................................................................................. 73<br />
Registers............................................................................................................. 76<br />
Keyboard Interface ............................................................................. 77<br />
Registers............................................................................................................. 78<br />
2-wire Interface (TWI) ......................................................................... 81<br />
Description.......................................................................................................... 83<br />
Notes .................................................................................................................. 86<br />
Registers............................................................................................................. 96<br />
Serial Port Interface (SPI)................................................................... 99<br />
Features.............................................................................................................. 99<br />
Signal Description............................................................................................... 99<br />
Functional Description ...................................................................................... 101<br />
Hardware Watchdog Timer .............................................................. 108<br />
Using the WDT ................................................................................................. 108<br />
WDT During Power Down and Idle................................................................... 109<br />
ONCE(TM) Mode (ON Chip Emulation) ........................................... 110<br />
Power-off Flag................................................................................... 111<br />
EEPROM <strong>Data</strong> Memory..................................................................... 112<br />
Write <strong>Data</strong>......................................................................................................... 112<br />
Read <strong>Data</strong>......................................................................................................... 114<br />
Registers........................................................................................................... 115<br />
157