MC68HC705C4ACB MOTOROLA [Motorola, Inc], MC68HC705C4ACB Datasheet - Page 120

• Manufacturer Part Number: MC68HC705C4ACB
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Serial Communications Interface (SCI)
10.5.2 Receiver
Technical Data
120
Figure 10-4
Figure 10-3
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Idle Characters — An idle character contains all logic 1s and has
no start or stop bits. Idle character length depends on the M bit in
SCCR1. The preamble is a synchronizing idle character that
begins every transmission.
Clearing the TE bit during a transmission relinquishes the
PD1/TDO pin after the last character to be transmitted is shifted
out. The last character may already be in the shift register, or
waiting in the SCDR, or it may be a break character generated by
writing to the SBK bit. Toggling TE from logic 0 to logic 1 while the
last character is in transmission generates an idle character (a
preamble) that allows the receiver to maintain control of the
PD1/TDO pin.
Transmitter Interrupts — These sources can generate SCI
transmitter interrupt requests:
– Transmit Data Register Empty (TDRE) — The TDRE bit in the
– Transmission Complete (TC) — The TC bit in the SCSR
Character Length — The receiver can accommodate either 8-bit
or 9-bit data. The state of the M bit in SCI control register 1
(SCCR1) determines character length. When receiving 9-bit data,
bit R8 in SCCR1 is the ninth bit (bit 8).
Serial Communications Interface (SCI)
SCSR indicates that the SCDR has transferred a character to
the transmit shift register. TDRE is a source of SCI interrupt
requests. The transmission complete interrupt enable bit
(TCIE) in SCCR2 is the local mask for TDRE interrupts.
indicates that both the transmit shift register and the SCDR are
empty and that no break or idle character has been generated.
TC is a source of SCI interrupt requests. The transmission
complete interrupt enable bit (TCIE) in SCCR2 is the local
mask for TC interrupts.
shows the structure of the SCI receiver. Refer to
for a summary of the SCI receiver I/O registers.
MC68HC705C4A • MC68HSC705C4A — Rev. 3.0
MOTOROLA