SERIAL I/O
7905 Group User’s Manual Rev.1.0
11-46
11.4 Clock asynchronous serial I/O (UART) mode
Fig. 11.4.8 Example of transmit timing when transfer data length = 8 bits (when parity enabled,
1 stop bit and selecting CTS function selected)
Fig. 11.4.7 Example of transmit timing when transfer data length = 8 bits (when parity enabled,
1 stop bit selected, CTS function not selected)
Tc
D0 D1 D2 D3
D4 D5 D6
D7
ST
P
SP
D0 D1
D0 D1 D2 D3 D4 D5 D6 D7
ST
P
ST
SP
TENDi
TxDi
TENDi: Next transmit conditions are examined when this signal level
becomes “H.”
(TENDi is an internal signal. Accordingly, it cannot be read from
the external.)
Tc: 16 (n + 1)/fi or 16 (n + 1)/fEXT
fi: BRGi’s count source frequency (internal clock)
fEXT: BRGi’s count source frequency (external clock)
n: Value set in 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.
Cleared to “0” when interrupt request is accepted or cleared to “0” by software.
The above timing diagram applies when
the following conditions are satisfied:
q Parity enabled
q 1 stop bit
q CTS function not selected
UARTi transmit register
← UARTi transmit buffer register
Stopped because transmit enable bit = “0”
ST: Start bit
0 to D7: Transfer data
P: Parity bit
ST: Stop bit
The above timing diagram applies
when the following conditions are
satisfied:
q Parity enabled
q 1 stop bit
q CTS function selected
Tc
D0 D1 D2 D3
D4 D5 D6
D7
ST
P
SP
D0 D1
D0 D1 D2 D3 D4 D5 D6 D7
ST
P SP
ST
TENDi
TxDi
TENDi: Next transmit conditions are examined when this signal level
becomes “H.”
(TENDi is an internal signal. Accordingly, it cannot be read from
the external.)
Tc = 16 (n + 1)/fi or 16 (n + 1)/fEXT
fi: BRGi’s count source frequency (internal clock)
fEXT: BRGi’s count source frequency (external clock)
n: Value set in BRGi
Transfer clock
Transmit buffer
empty flag
Transmit register
empty flag
UARTi transmit
interrupt request bit
Data is set in UARTi transmit buffer register.
Cleared to “0” when interrupt request is accepted or cleared to “0” by software.
UARTi transmit register
← UARTi transmit buffer register
Transmit enable bit
CTSi
Stopped because CTSi = “H”
ST: Start bit
D0 to D7: Transfer data
P: Parity bit
ST: Stop bit
Stopped because transmit
enable bit = “0”