Baud Rate By External Clock; Fig. 12.13 Baud Rate Selector By External Clock - Fujitsu MB90420/5 (A) Series Hardware Manual

F2mc-16lx family 16-bit microcontrollers

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12.6.3 Baud Rate by External Clock

The setting when selecting the external clock as the transfer clock of the UART and the baud rate calculation

are shown below.

n Baud rate by external clock

To select a baud rate by the external clock, the following three settings are required:

• Write 111B to the CS2 to CS0 bits of the mode register (SMR0/1), to select the baud rate the external

clock input.

• Set the SCK0/P02 pin and SCK1/P05 pin to the input (DDR0: bit 2 = 0, bit 5 = 0)

• Write 0 to the SCKE bit of the mode register (SMR0/1), to make the pin serve as an external clock input

As shown in Figure 12.13, the baud rate is selected based on the external clock input from the SCK0 pin.

Since the internal division ratio is fixed, the cycle of the external input clock must be changed to change the

• Expressions to obtain baud rate

Asynchronous baud rate = f/16

Synchronous baud rate = f

f : External clock frequency (2 MHz at max.)

SMR0/1: CS2 to CS0 = 111

(Selection of external clock)

(Selection of clock synchronous/asynchronous mode)

Clock selector

1/1 (synchronous)

1/16 (asynchronous)