跳转到主内容
Knowledgebase
Home
Renesas Electronics China - Knowledgebase

Why problems occur when programming via uPD78F9116 UART with 4.19 MHz?

Latest Updated:12/01/2011

Question:

I have problems with programming via the uPD78F9116's UART using the 4.19 MHz frequency.
However, there is no problem when I set the frequency to 5MHz.

Answer:

The parameters required for the baud rate setting are determined by measuring the pulse width of the 00 data transmit signal from the programmer.
At this time, the CPU performs time measurement by firmware and sets the baud rate parameter to the BRGC register.

The baud rate and the setting value, as well as the error for each clock, are as follows.

Baud Rate BRGC 5.0MHz 4.9152MHz 4.1943MHz
9600 40H 1.73% 0 -14.6%
19200 30H 1.73% 0 -14.6%

In other words, when using a 4.1943MHz clock, the error is too large for use.

Suitable Products