7906 datasheet(263/531 Pages) RENESAS

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SERIAL I/O

7906 Group User’s Manual Rev.2.0

11-22

11.3 Clock synchronous serial I/O mode

11.3.2 Transfer data format

LSB first or MSB first can be selected as the transfer data format. Table 11.3.3 lists the relationship

between the transfer data format and writing/reading to and from the UARTi transmit/receive buffer register.

The transfer format select bit (bit 7 at addresses 3416, 3C16) selects the transfer data format. When this bit

is cleared to “0,” the set data is written to the UARTi transmit buffer register as the transmit data, as it is.

Similarly, the data in the UARTi receive buffer register is read out as the receive data, as it is. (See the

upper row in Table 11.3.3.) When this bit is set to “1,” each bit’s position of set data is reversed, and the

resultant data will be written to the UARTi transmit buffer register as the transmit data. Similarly, each bit’s

position of data in the UARTi receive buffer register is reversed, and the resultant data will be read out

as the receive data. (See the lower row in Table 11.3.3.)

Note that only the method of writing/reading to and from the UARTi transmit/receive buffer register is

affected by selection of the transfer data format, and that the transmit/receive operation is unaffected by

it.

Table 11.3.3 Relationship between transfer data format and writing/reading to and from UARTi transmit/

receive buffer register

Writing to UARTi transmit buffer

Reading from UARTi receive

buffer register

Data bus

UARTi transmit

buffer register

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

Data bus

UARTi receive

buffer register

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

LSB

(Least Significant Bit)

first

Data bus

UARTi transmit

buffer register

Data bus

UARTi receive

buffer register

MSB

(Most Significant Bit)

first

Transfer data format

Transfer format

select bit

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

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