AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 104

• Manufacturer Part Number: AT89C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 2
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

24.8.3
24.9
24.9.1
24.9.2
24.9.3
104
Flow Description
AT89C51RD2/ED2
Checksum Error
Overview
Communication Initialization
Autobaud Performances
The Full Chip Erase does not affect the bootloader.
When a checksum error is detected, send ‘X’ followed with CR&LF.
An initialization step must be performed after each Reset. After microcontroller reset, the boot-
loader waits for an autobaud sequence (see section ‘Autobaud Performances’).
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
web site.
The host initializes the communication by sending a ’U’ character to help the bootloader to com-
pute the baudrate (autobaud).
Figure 24-7. Initialization
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 program 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 AT89C51RD2/ED2 to establish the baud rate. Table show the
autobaud capability.
Table 24-8.
Frequency
(MHz)
Baudrate (kHz)
2400
• SBV = FCh
• SSB = FFh
Autobaud Performances
Communication Opened
Init Communication
Else
If (Not Received "U")
1.8432
Host
OK
OK
2
2.4576
OK
OK
3
"U"
3.6864
"U"
OK
OK
4
Performs Autobaud
Sends Back “U” Character
OK
5
Bootloader
OK
4235K–8051–05/08
6
7.3728
OK