MC68HC05C8A Datasheet, PDF (55/116 Pages) Motorola, Inc – Microcontrollers

SCI Input/Output (I/O) Registers
RE — Receive Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver and receiver
interrupts but does not affect the receiver interrupt flags. Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
RWU — Receiver Wakeup Enable Bit
This read/write bit puts the receiver in a standby state. Typically, data transmitted to the receiver clears
the RWU bit and returns the receiver to normal operation. The WAKE bit in SCCR1 determines
whether an idle input or an address mark brings the receiver out of the standby state. Reset clears the
RWU bit.
1 = Standby state
0 = Normal operation
SBK — Send Break Bit
Setting this read/write bit continuously transmits break codes in the form of 10-bit or 11-bit groups of
logic 0s. Clearing the SBK bit stops the break codes and transmits a logic 1 as a start bit. Reset clears
the SBK bit.
1 = Break codes being transmitted
0 = No break codes being transmitted
9.5.4 SCI Status Register
The SCI status register contains flags to signal these conditions:
• Transfer of SCDR data to transmit shift register complete
• Transmission complete
• Transfer of receive shift register data to SCDR complete
• Receiver input idle
• Receiver overrun
• Noisy data
• Framing error
Address: $0010
Bit 7
6
5
4
3
2
1
Bit 0
Read: TDRE
TC
RDRF
IDLE
OR
NF
FE
0
Write:
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-7. SCI Status Register (SCSR)
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
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A Data Sheet, Rev. 5.1
Freescale Semiconductor
55