7641 datasheet(34/138 Pages) RENESAS

34 / 138 page

7641 Group

Rev.4.00

Aug 28, 2006

page 34 of 135

REJ03B0191-0400

UTXD output (P84/UTXD1,

P80/UTXD2/SRDY)

Transfer clock

Tranmit enable bit

Transmit buffer

empty flag

Transmit complete flag

Data set into UARTx transmit buffer register 1

Data transferring from UARTx transmit

buffer register 1 to Transmit shift register 1

This timing applies to the conditions:

•Character length = 8 bits

•Parity enabled

•1 stop bit

qRTS (Request-to-Send) Function

As a receiver, the UART can be configured to generate the Re-

quest-to-Send (RTSx) handshaking signal. This is enabled by

setting the RTS Function Enable Bit (bit 6 of UxCON) to “1”.

When reception is enabled, that is the Receive Enable Bit is “1”,

the RTSx pin goes “L” to inform a transmitter that reception is pos-

sible. The RTSx pin goes “H” at reception starting and does “L” at

receiving of the last bit.

The delay time from the reception of the last stop bit to the asser-

tion of RTSx is selectable using the RTS Assertion Delay Count

Select Bits.

BRGx (x = 1, 2)

count source

URXD (P85/URXD1,

P81/URXD2/SCLK)

RTSx pin (P87/RTS1,

P83/RTS2/STXD)

Receive enable bit

Receive buffer

empty flag

Transfer clock

Transfer clock generated at falling edge

of start bit and receive started

Receive data latched

Data transferring from UARTx receive register

1 to Receive buffer register 1 (Note)

Note: When no RTS assertion delay, the RTSx pin goes “L”.

The RTS assertion delay counts are selected by bits 4 to 7 of UARTx RTS control register.

This timing applies to the conditions:

•Character length = 8 bits

•Parity enabled

•1 stop bit

Fig. 28 UARTx transmit timing (CTS function disbled)

When the Receive Enable Bit is set to “0” or the Receive initializa-

tion bit is set to “1”, the RTSx pin goes “H”. Even when the

Receive Enable Bit is set to “1”, the RTSx pin goes “H” if detecting

an invalid start bit.

Figure 29 shows the UARTx receive timing.

Fig. 29 UARTx transmit timing (RTS function enabled)

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