Datasheet
Table Of Contents
- Features
- Description
- Block Diagram
- SFR Mapping
- Pin Configurations
- Oscillators
- Enhanced Features
- Dual Data Pointer Register DPTR
- Expanded RAM (XRAM)
- Reset
- Power Monitor
- Timer 2
- Programmable Counter Array PCA
- Serial I/O Port
- Interrupt System
- Power Management
- Keyboard Interface
- 2-wire Interface (TWI)
- Serial Port Interface (SPI)
- Hardware Watchdog Timer
- ONCE(TM) Mode (ON Chip Emulation)
- Power-off Flag
- EEPROM Data Memory
- Reduced EMI Mode
- Flash Memory
- Electrical Characteristics
- Absolute Maximum Ratings
- DC Parameters
- AC Parameters
- Explanation of the AC Symbols
- External Program Memory Characteristics
- External Program Memory Read Cycle
- External Data Memory Characteristics
- External Data Memory Write Cycle
- External Data Memory Read Cycle
- Serial Port Timing - Shift Register Mode
- Shift Register Timing Waveforms
- External Clock Drive Waveforms
- AC Testing Input/Output Waveforms
- Float Waveforms
- Clock Waveforms
- Ordering Information
- Packaging Information
- Table of Contents
15
AT89C51ID2
4289C–8051–11/05
Table 17. OSCCON Register (for AT8xC51Ix2 only)
OSCCON- Oscillator Control Register (86h)
Reset Value = XXXX X0’HSB.OSC
’’HSB.OSC’b (see Hardware Security Byte (HSB))
Not bit addressable
Table 18. CKRL Register
CKRL - Clock Reload Register
Reset Value = 1111 1111b
Not bit addressable
76543210
- - - - - SCLKT0 OscBEn OscAEn
Bit
Number
Bit
Mnemonic Description
7-Reserved
6-Reserved
5-Reserved
4-Reserved
3-Reserved
2SCLKT0
Sub Clock Timer0
Cleared by software to select T0 pin
Set by software to select T0 Sub Clock
Cleared by hardware after a Power Up
1 OscBEn
OscB enable bit
Set by software to run OscB
Cleared by software to stop OscB
Programmed by hardware after a Power-up regarding HSB.OSC (Default
cleared, OSCB stopped)
0 OscAEn
OscA enable bit
Set by software to run OscA
Cleared by software to stop OscA
Programmed by hardware after a Power-up regarding HSB.OSC(Default Set,
OSCA runs)
76543210
--------
Bit
Number Mnemonic Description
7:0 CKRL
Clock Reload Register:
Prescaler value