Intel MCS 51

8051,8052 and 80C51
CONTENTS
PAGE
INTRODUCTION........................................ 3-3
Special Function Registers......................... 3-3
PORT STRUCTURES AND
OPERATION........................................... 3-6
[/0 Configurations....................................... 3-7
Writing to a Port.......................................... 3-7
Port Loadingand Interfacing ...................... 3-8
Read-Modify-Write Feature ........................ 3-9
ACCESSING EXTERNAL MEMORY.........3-9
TIMEWCOUNTERS ................................... 3-9
Timer Oand Timer 1.................................. 3-10
Timer 2...................................................... 3-12
SERIAL INTERFACE............................... 3-13
Multiprocessor Communications .............. 3-14
Serial Port Control Register...................... 3-14
Baud Rates...............................................3-15
More About Mode O.................................. 3-17
More About Mode 1.................................. 3-17
More About Modes 2 and 3 ...................... 3-20
Hardware Description
CONTENTS
PAGE
INTERRUPTS........................................... 3-23
Priority Level Structure ............................. 3-24
How Interrupts Are Handled..................... 3-24
External Interrupts .................................... 3-25
ResponseTime......................................... 3-25
SINGLE-STEP OPERATION.................... 3-26
RESET...................................................... 3-26
POWER-ON RESET................................. 3-27
POWER-SAVING MODES OF
OPERATfON
......................................... 3-27
CHMOS Power Reduction Modes ............ 3-27
EPROM VERSIONS .................................3-29
Exposure to Light...................................... 3-29
Program Memory Locks ........................... 3-29
ONCE Mode
............................................. 3-30
THE ON-CHIP OSCILLATORS................3-30
HMOS Versions ........................................ 3-30
CHMOS Versions
..................................... 3-32
INTERNAL TIMING .................................. 3-33
3-1