Freescale Semiconductor, Inc.
Serial Communications Interface (SCI)
TDRE — Transmit Data Register Empty 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.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
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.
1 = No transmission in progress
0 = Transmission in progress
RDRF — Receive Data Register Full Bit
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.
1 = Received data available in SCDR
0 = Received data not available in SCDR
IDLE — Receiver Idle 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 = Receiver input idle
0 = Receiver input not idle
Technical Data
134
MC68HC705C8A — Rev. 3
Serial Communications Interface (SCI)
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