7733 datasheet(229/940 Pages) RENESAS

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SERIAL I/O

7733 Group User’s Manual

8–26

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

Transfer format

selection bit

Transfer data format

When data is written to UARTi

transmission buffer register

When data is read from UARTi

receive buffer register

LSB

(Least Significant Bit)

first

Data bus

UARTi transmission

buffer register

Data bus

UARTi receive

buffer register

MSB

(Most Significant Bit)

first

Data bus

UARTi transmission

buffer register

Data bus

UARTi receive

buffer register

8.3.2 Transfer data format

LSB-first or MSB-first can be selected (UART0, UART1). Table 8.3.5 lists the relationship between the

transfer data format and the way to write/read to and from the UARTi transmission/receive buffer register.

By setting the transfer format selection bit (bit 7 at addresses 3416, 3C16), transfer data format can be

selected.

When this bit is cleared to “0,” the set data is written to the UARTi transmission buffer register as the

transmit data. Similarly, the data in the UARTi receive buffer register is read out as the receive data. (Refer

to the upper row in Table 8.3.5.)

When this bit is set to “1,” each bit’s position of the set data is reversed, and then this data is written to

the UARTi transmission buffer register as the transmit data. Similarly, each bit’s position of data in the

UARTi receive buffer register is reversed, and then this data is read out as the receive data. (Refer to the

lower row in Table 8.3.5.)

Note that only the way to write/read to and from the UARTi transmission/receive buffer register is affected

by the transfer data format. The transmit/receive operation is unaffected.

The transfer data format for UART2 is fixed to “LSB-first.”

Table 8.3.5 Relationship between transfer data format and way to write/read to and from UARTi

transmission/receive buffer register

8.3 Clock synchronous serial I/O mode

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