
7702/7703 Group User’s Manual
7–45
SERIAL I/O
7.4 Clock asynchronous serial I/O (UART) mode
Fig. 7.4.6 Example of transmit timing when transfer data length is 8 bits (when parity enabled,
selecting 1 stop bit)
Fig. 7.4.7 Example of transmit timing when transfer data length is 9 bits (when parity disabled,
selecting 2 stop bits)
Tc
D0 D1
D2 D3 D4
D5 D6 D7
ST
P
SP
D0 D1
D2 D3 D4
D5 D6 D7
ST
P
SP
ST
TENDi
TxDi
CTSi
“0”
“1”
“0”
“1”
“L”
“H”
“0”
“1”
“0”
“1”
TENDi: Next transmit conditions are examined when this signal level is “H.”
(TENDi is an internal signal. Accordingly, it cannot be read from an external.)
Tc: 16(n + 1)/fi or 16(n + 1)/fEXT
fi: BRGi count source frequency (f2, f16, f64, f512)
fEXT: BRGi count source frequency (external clock)
n: Value set to BRGi
Transfer clock
Transmit enable bit
Transmit buffer
empty flag
Transmit register
empty flag
UARTi transmit
interrupt request bit
Data is set in UARTi transmit buffer register.
Start bit
Parity bit
Cleared to “0” when interrupt request is accepted or cleared by software.
The above timing diagram applies to
the following conditions:
q Parity enabled
q 1 stop bit
q CTS function selected
UARTi transmit register
UARTi transmit buffer register
Stopped because transmit enable bit = “0”
Stop bit
D0 D1
D2 D3 D4
D5 D6 D7
ST
D8
D0 D1
D2 D3 D4
D5 D6 D7
ST
SP
D0 D1
ST
D8
SP
SP SP
“0”
“1”
“0”
“1”
“0”
“1”
Tc
“0”
“1”
TENDi
TxDi
TENDi: Next transmit conditions are examined when this signal level is “H.”
(TENDi is an internal signal. Accordingly, it cannot be read from an external.)
Tc: 16(n + 1)/fi or 16(n + 1)/fEXT
fi: BRGi count source frequency (f2, f16, f64, f512)
fEXT: BRGi count source frequency (external clock)
n: Value set to BRGi
Transfer clock
Transmit enable bit
Transmit buffer
empty flag
Transmit register
empty flag
UARTi transmit
interrupt request bit
Data is set in UARTi transmit buffer register.
Start bit
Cleared to “0” when interrupt request is accepted or cleared by software.
The above timing diagram applies to
the following conditions:
q Parity disabled
q 2 stop bits
q CTS function disabled
UARTi transmit register
UARTi transmit buffer register
Stopped because transmit enable bit = “0”
Stop bit