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 11.4.2. Bits 4 to 6 at addresses
3016 and 3816 select the transfer data format. (See Figure 11.2.2.) Set the same transfer data format for both
transmitter and receiver sides.
Figure 11.4.3 shows an example of transfer data format. Table 11.4.5 lists each bit in transmit data.
Transfer data length of 7 bits
Transfer data length of 8 bits
Transfer data length of 9 bits
1ST—7DATA
1ST—7DATA
1ST—7DATA—1PAR—1SP
1ST—7DATA—1PAR—2SP
1SP
2SP
1ST—8DATA
1ST—8DATA
1ST—8DATA—1PAR—1SP
1ST—8DATA—1PAR—2SP
1SP
2SP
1ST—9DATA
1ST—9DATA
1SP
2SP
ST
: Start bit
DATA : Character bit (Transfer data)
PAR : Parity bit
1ST—9DATA—1PAR—1SP
1ST—9DATA—1PAR—2SP
SP
: Stop bit
Fig. 11.4.2 Transfer data format
• 1ST–8DATA–1PAR–1SP
Time
Transmit/Receive data
DATA (8 bits)
Next transmit/receive data
(When continuously
transferred)
ST LSB
MSB PAR SP
ST
Fig. 11.4.3 Example of transfer data format
Table 11.4.5 Each bit in transmit data
Name
Functions
ST
“L” signal equivalent to 1 character bit. This is added immediately before the character
bits. It indicates start of data transmission.
Start bit
DATA
Transmit data which is set in the UARTi transmit buffer register.
Character bit
PAR
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 the sum of this bit and character bits is always
an odd or even number.
Parity bit
SP
“H” level signal equivalent to 1 or 2 character bits. This is added immediately after
the character bits (or parity bit when parity is enabled). It indicates completion of
data transmission.
Stop bit
7906 Group User’s Manual Rev.2.0
11-39
RENESAS [ RENESAS TECHNOLOGY CORP ]
