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
AT89C51RB2/RC2 to establish the baud rate. Table 72 shows the autobaud capability.
Table 72. Autobaud Performances
Frequency (MHz)
Baudrate (bit/s)
1.8432
2
2.4576
OK
OK
OK
OK
OK
-
3
3.6864
OK
OK
OK
OK
OK
OK
-
4
OK
OK
OK
-
5
6
7.3728
OK
8
2400
OK
OK
OK
OK
-
OK
OK
OK
OK
OK
OK
OK
OK
-
OK
OK
OK
OK
OK
-
OK
OK
OK
OK
4800
-
-
-
-
-
-
OK
9600
OK
19200
38400
57600
115200
OK
-
OK
-
OK
-
-
-
-
OK
-
-
-
-
-
OK
Frequency (MHz)
Baudrate (bit/s)
10
OK
OK
OK
OK
-
11.0592
OK
12
OK
OK
OK
OK
OK
-
14.318
OK
14.746
OK
16
20
24
26.6
OK
OK
OK
OK
OK
OK
-
2400
OK
OK
OK
OK
OK
OK
-
OK
OK
OK
OK
OK
OK
-
OK
OK
OK
OK
OK
OK
-
4800
OK
OK
OK
9600
OK
OK
OK
19200
38400
57600
115200
OK
OK
OK
OK
OK
OK
-
OK
OK
OK
-
OK
-
OK
OK
Command Data Stream
Protocol
All commands are sent using the same flow. Each frame sent by the host is echoed by
the bootloader.
98
AT89C51RB2/RC2
4180E–8051–10/06
ATMEL [ ATMEL ]
