Datasheet

98
AT89C51RB2/RC2
4180D–8051–06/05
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.
Command Data Stream
Protocol
All commands are sent using the same flow. Each frame sent by the host is echoed by
the bootloader.
Table 72. Autobaud Performances
Frequency (MHz)
Baudrate (bit/s) 1.8432 2 2.4576 3 3.6864 4 5 6 7.3728 8
2400 OK OK OK OK OK OK OK OK OK OK
4800 OK - OK OK OK OK OK OK OK OK
9600 OK - OK OK OK OK OK OK OK OK
19200 OK - OK OK OK - - OK OK OK
38400 - - OK OK - OK OK OK
57600 - - - - OK - - - OK
115200 - - - - - - - - OK
Frequency (MHz)
Baudrate (bit/s) 10 11.0592 12 14.318 14.746 16 20 24 26.6
2400 OK OK OK OK OK OK OK OK OK
4800 OK OK OK OK OK OK OK OK OK
9600 OK OK OK OK OK OK OK OK OK
19200 OK OK OK OK OK OK OK OK OK
38400 - OK OK OK OK OK OK OK OK
57600 - OK - OK OK OK OK OK OK
115200 - OK - OK OK - - - -