at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 57

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Protocol
Overview
Communication Initialization
Autobaud Performances
Command Data Stream Protocol
Figure 6. Command Flow
40
Sends frame (made of 2 ASCII
characters per Byte)
Echo analysis
AT89C51RE2
Sends first character of the
Frame
Host
An initialization step must be performed after each Reset. After microcontroller reset,
t h e bo o t l o a d e r w a i t s f o r a n a u t o b a ud s e q ue n c e ( s e e S e c t i o n “ A u to b a u d
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 compute the baudrate (autobaud).
Figure 5. Initialization
The bootloader supportsa wide range of baud rates. 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. Table 30 shows the autobaud
capabilities.
All commands are sent using the same flow. To increase performance, the echo has
been removed from the bootloader response.
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
Bootloader
7663B–8051–03/07