Datasheet

136
4235K–8051–05/08
AT89C51RD2/ED2
14 Serial I/O Port ......................................................................................... 48
14.1 Framing Error Detection ..................................................................................48
14.2 Automatic Address Recognition ......................................................................49
14.3 Registers .........................................................................................................51
14.4 Baud Rate Selection for UART for Mode 1 and 3 ............................................51
14.5 UART Registers ...............................................................................................54
15 Keyboard Interface ................................................................................ 59
15.1 Registers .........................................................................................................60
16 Serial Port Interface (SPI) ...................................................................... 63
16.1 Features ..........................................................................................................63
16.2 Signal Description ............................................................................................63
16.3 Functional Description .....................................................................................65
17 Interrupt System .................................................................................... 72
17.1 Registers .........................................................................................................73
17.2 Interrupt Sources and Vector Addresses .........................................................73
18 Power Management ............................................................................... 80
18.1 Introduction ......................................................................................................80
18.2 Idle Mode .........................................................................................................80
18.3 Power-Down Mode ..........................................................................................81
18.4 Registers .........................................................................................................83
19 Hardware Watchdog Timer ................................................................... 84
19.1 Using the WDT ................................................................................................84
19.2 WDT during Power-down and Idle ...................................................................85
20 ONCE
®
Mode (ON- Chip Emulation) ..................................................... 86
21 Power-off Flag ........................................................................................ 87
22 Reduced EMI Mode ................................................................................ 88
23 EEPROM Data Memory .......................................................................... 89
23.1 Write Data ........................................................................................................89
23.2 Read Data .......................................................................................................90
23.3 Registers .........................................................................................................91
24 Flash/EEPROM Memory ........................................................................ 93
24.1 Features ..........................................................................................................93
24.2 Flash Programming and Erasure .....................................................................93