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
129
AT89C51ID2
4289C–8051–11/05
Flow Description
Overview An initialization step must be performed after each Reset. After microcontroller reset,
the bootloader waits for an autobaud sequence ( see section ‘autobaud performance’).
When the communication is initialized the protocol depends on the record type
requested by the host.
FLIP, a software utility to implement ISP programming with a PC, is available from the
Atmel the web site.
Communication Initialization The host initializes the communication by sending a ’U’ character to help the bootloader
to compute the baudrate (autobaud).
Figure 51. Initialization
Autobaud Performances The ISP feature allows a wide range of baud rates in the user application. It is also
adaptable to a wide range of oscillator frequencies. This is accomplished by measuring
the bit-time of a single bit in a received character. This information is then used to pro-
gram the baud rate in terms of timer counts based on the oscillator frequency. The ISP
feature requires that an initial character (an uppercase U) be sent to the AT89C51ID2 to
establish the baud rate. Table show the autobaud capability.
Host
Bootloader
"U"
Performs autobaud
Init communication
If (not received "U")
"U"
Communication opened
Else
Sends back U character
Table 95. Autobaud Performances
Frequency (MHz)
Baudrate (kHz) 1.8432 2 2.4576 3 3.6864 4 5 6 7.3728
2400 OKOKOKOKOKOKOKOKOK
4800 OK - OK OK OK OK OK OK OK
9600 OK - OK OK OK OK OK OK OK
19200 OK - OKOKOK - - OKOK
38400 - - OK OK - OK OK OK
57600 - - - - OK - - - OK
115200 --------OK
Frequency (MHz)
Baudrate (kHz) 8 10 11.0592 12 14.746 16 20 24 26.6
2400 OKOKOKOKOKOKOKOKOK