m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 287

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

SERIAL I/O
11.3 Clock synchronous serial I/O mode
Fig. 11.3.10 Connection example
11-32
11.3.6 Receive operation
In the case of an internal clock selected, when the receive conditions described in section “11.3.5 Method
of reception” have been satisfied, a transfer clock is generated and the reception is started after 1 cycle
of the transfer clock or less has passed. In the case of an external clock selected, when the receive
conditions have been satisfied, the UARTi enters the receive-enabled state, and then reception will be
started when an external clock is input to the CLKi pin.
In the case of an external clock selected, when connecting the RTS
side, the timing of transmission and that of reception can be matched. In the case of an internal clock
selected, do not use the RTS function. It is because the RTS output is undefined in the case of an internal
clock selected.
In the case of an external clock and the RTS function selected, the RTS
described below.
When the receive enable bit = “0,” if one of the following is performed, the RTS
“L” and informs of the transmitter side that reception has become enabled:
• The receive enable bit is set to “1.”
• The low-order byte of the UARTi receive buffer register is read out.
When the receive enable bit = “1,” if the low-order byte of the UARTi receive buffer register is read out,
the RTS
Accordingly, when performing reception continuously, an overrun occurrence can be avoided because the
RTS output level does not become “L” until the receive data is read out.
When reception has started, the RTS
Figure 11.3.10 shows a connection example.
i
pin’s output level becomes “L.”
Transmitter side
CLK
CTS
RxD
TxD
7905 Group User’s Manual Rev.1.0
i
pin’s output level becomes “H.”
i
i
i
i
RTS
TxD
RxD
CLK
Receiver side
i
i
i
i
i
pin to the CTS
i
pin’s output level becomes as
i
pin’s output level becomes
i
pin of the transmitter