AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 57

• Manufacturer Part Number: AT89C51RE2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RE2

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Uart: 2
• Sram (kbytes): 8.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/OCD
• Watchdog: Yes

Protocol
Overview
Communication
Initialization
Autobaud
Performances
Command Data Stream Protocol
Figure 22. Command Flow
7663E–8051–10/08
Sends frame (made of 2 ASCII
characters per Byte)
Echo analysis
Sends first character of the
Frame
Host
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 issued by the
host.
The host initiates the communication by sending a ’U’ character to help the bootloader to com-
pute the baudrate (autobaud).
Figure 21. Initialization
The bootloader supports a wide range of baud rates. It is also adaptable to a wide range of oscil-
lator 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.
All commands are sent using the same flow. To increase performance, the echo has been
removed from the bootloader response.
Each command flow may end with:
Communication Opened
Init Communication
Else
If (not received “U”)
Host
":"
":"
Gets frame, and sends back echo
for each received Byte
“U”
“U”
Else
If (not received ":")
Sends echo and start
reception
Bootloader
Sends Back ‘U’ Character
Performs Autobaud
AT89C51RE2
Bootloader
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