MC68HC705C9A Datasheet, PDF (68/118 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface (SCI)
$0010 Bit 7
6
5
4
3
2
1
Bit 0
Read:
TDRE
TC
RDRF
IDLE
OR
NF
FE
Write:
Reset: 1
1
0
0
0
0
0
—
= Unimplemented
Figure 9-11. SCI Status Register (SCSR)
TDRE — Transmit Data Register Empty Flag
This clearable, read-only flag 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 the transmitter on.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Flag
This clearable, read-only flag is set when the TDRE bit is set, and no data, preamble, or break
character is being transmitted. TDRE 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
the transmitter on.
1 = No transmission in progress
0 = Transmission in progress
RDRF — Receive Data Register Full Flag
This clearable, read-only flag 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 the SCCR2 is also set. Clear the RDRF
bit by reading the SCSR with RDRF set and then reading the SCDR.
1 = Received data available in SCDR
0 = Received data not available in SCDR
IDLE — Receiver Idle Flag
This clearable, read-only flag is set when 10 or 11 consecutive logic 1s appear on the receiver input.
IDLE generates an interrupt request if the ILIE bit in the SCCR2 is also set. Clear the ILIE bit by reading
the SCSR with IDLE set and then reading the SCDR.
1 = Receiver input idle
0 = Receiver input not idle
OR — Receiver Overrun Flag
This clearable, read-only flag is set if the SCDR is not read before the receive shift register receives
the next word. OR generates an interrupt request if the RIE bit in the SCCR2 is also set. The data in
the shift register is lost, but the data already in the SCDR is not affected. Clear the OR bit by reading
the SCSR with OR set and then reading the SCDR.
1 = Receive shift register full and RDRF = 1
0 = No receiver overrun
NF — Receiver Noise Flag
This clearable, read-only flag is set when noise is detected in data received in the SCI data register.
Clear the NF bit by reading the SCSR and then reading the SCDR.
1 = Noise detected in SCDR
0 = No noise detected in SCDR
MC68HC05C9A Advance Information Data Sheet, Rev. 4.1
68
Freescale Semiconductor