Flash memory In-Application Programming

Power-On reset code execution
Following reset, the P89V51RD2 will either enter the Soft ICE mode (if previously enabled via ISP command) or attempt to auto baud to the ISP boot loader. If this auto baud is not successful within about 400 ms, the device will begin execution of the user code.


Using the In-System Programming
The ISP feature allows for a wide range of baud rates to be used in your application, independent of the oscillator frequency. 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 P89V51RD2 to establish the baud rate. The ISP firmware provides auto-echo of received characters. Once baud rate initialization has been performed, the ISP firmware will only accept Intel Hex-type records.