7721 datasheet(236/577 Pages) RENESAS

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7721 Group User’s Manual

11–33

SERIAL I/O

11.4 Clock asynchronous serial I/O (UART) mode

11.4.2 Transfer data format

The transfer data format can be selected from formats shown in Figure 11.4.1. Bits 4 to 6 at addresses

3016 and 3816 select the transfer data format. (Refer to “Figure 11.2.2.”) Set the same transfer data format

for both transmitter and receiver sides.

Figure 11.4.2 shows an example of transfer data format. Table 11.4.5 lists each bit in transmit data.

Transfer data length of 7 bits

1ST—7DATA

1SP

1ST—7DATA

2SP

1ST—7DATA—1PAR— 1SP

1ST—7DATA—1PAR— 2SP

Transfer data length of 8 bits

1ST—8DATA

1SP

1ST—8DATA

2SP

1ST—8DATA—1PAR— 1SP

1ST—8DATA—1PAR— 2SP

Transfer data length of 9 bits

1ST—9DATA

1SP

1ST—9DATA

2SP

1ST—9DATA—1PAR— 1SP

1ST—9DATA—1PAR— 2SP

: Start bit

DATA : Character bit (Transfer data)

PAR

: Parity bit

: Stop bit

Fig. 11.4.1 Transfer data format

Name

Start bit

DATA

Character bit

PAR

Parity bit

Stop bit

Functions

“L” signal equivalent to 1 character bit which is added immediately before the

character bits. It indicates start of data transmission.

Transmit data which is set in the UARTi transmit buffer register.

A signal that is added immediately after the character bits in order to improve data

reliability. The level of this signal changes according to selection of odd/even parity

in such a way that the sum of “1”s in this bit and character bits is always an odd

or even number.

“H” level signal equivalent to 1 or 2 character bits which is added immediately after

the character bits (or parity bit when parity is enabled). It indicates finish of data

transmission.

Fig. 11.4.2 Example of transfer data format

Table 11.4.5 Each bit in transmit data

Time

•For the case where 1ST–8DATA–1PAR–1SP

LSB

MSB PAR

Transmit/Receive data

DATA (8 bits)

Next transmit/receive data

(When continuously

transferring)

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