NEC PD78P214 Manuale Utente

254

µ

PD78214 Sub-Series

The baud rate can be set by three methods listed in Table 9-2.

The table indicates the ranges of baud rates that can be generated by each method, the baud rate calculation
formulas, and the selection methods.

j

PRS3-PRS0

0H

1H

2H

3H

4H

5H

6H

7H

0

1

2

3

4

5

6

Baud rate clock source

f

ASCK

2048

–

f

ASCK

16

Selection method

Calculation formula

Baud rate range

×

2

n

×

1

16

f

ASCK

×

1

16

×

1

2

m + 1

f

CLK

2

j + 3

SCK of the ASIM register = 0

8-bit timer/counter 3

ASCK input

MDL0 through MDL3 of

the BRGC register = FH

Baud rate

generator

for UART

Internal

system clock

SCK of the ASIM

register = 1

CE of the BRGC

register = 1

MDL0 through MDL3 of the

BRGC register = 0H to EH

f

CLK

61440

–

f

CLK

64

×

1

n

×

1

16

f

CLK

K + 1

–

f

CLK

256

f

CLK

4194304

f

CLK

: Internal system clock frequency

k

: Value set in the MDL3 through MDL0 bits of the BRGC register (k = 1 through 14; see Fig. 9-9.)

1/n

: Frequency divider tap (n = 2, 4, 8, 16, 32, 64, 128, 256)

f

ASCK

: Frequency of the ASCK input clock (0 – f

CLK

/24)

1/16 : Serial data sampling rate

j

: Value set in the PRS3 through PRS0 bits of prescaler mode register 0 (j = 0 through 6)

m

: Value set in the 8-bit compare register (CR30); m = 0 through 255

Note   0 – f

CLK

/384 if the f

ASCK

 input range is included.

This section shows examples of setting the BRGC register when the baud rate generator for UART is used.

To use the baud rate generator, set the SCK bit of the asynchronous serial interface mode register (ASIM) to 1.