MC68HC705 MOTOROLA [Motorola, Inc], MC68HC705 Datasheet - Page 132

• Manufacturer Part Number: MC68HC705
• Description: HCMOS Microcontroller Unit
• Manufacturer: MOTOROLA [Motorola, Inc]

Serial Communications Interface (SCI)
Technical Data
132
TDRE — Transmit Data Register Empty Bit
TC — Transmission Complete Bit
RDRF — Receive Data Register Full Bit
IDLE — Receiver Idle Bit
This clearable, read-only bit is set when the data in the SCDR
transfers to the transmit shift register. TDRE generates an interrupt
request if the TIE bit in SCCR2 is also set. Clear the TDRE bit by
reading the SCSR with TDRE set and then writing to the SCDR. Reset
sets the TDRE bit. Software must initialize the TDRE bit to logic 0 to
avoid an instant interrupt request when turning on the transmitter.
This clearable, read-only bit is set when the TDRE bit is set and no
data, preamble, or break character is being transmitted. TC generates
an interrupt request if the TCIE bit in SCCR2 is also set. Clear the TC
bit by reading the SCSR with TC set and then writing to the SCDR.
Reset sets the TC bit. Software must initialize the TC bit to logic 0 to
avoid an instant interrupt request when turning on the transmitter.
This clearable, read-only bit is set when the data in the receive shift
register transfers to the SCI data register. RDRF generates an
interrupt request if the RIE bit in SCCR2 is also set. Clear the RDRF
bit by reading the SCSR with RDRF set and then reading the SCDR.
Reset clears the RDRF bit.
This clearable, read-only bit is set when 10 or 11 consecutive logic 1s
appear on the receiver input. IDLE generates an interrupt request if
the ILIE bit in SCCR2 is also set. Clear the IDLE bit by reading the
SCSR with IDLE set, and then reading the SCDR. Reset clears the
IDLE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
1 = No transmission in progress
0 = Transmission in progress
1 = Received data available in SCDR
0 = Received data not available in SCDR
1 = Receiver input idle
0 = Receiver input not idle
Serial Communications Interface (SCI)
MC68HC705C8A — Rev. 2.0
MOTOROLA