CM68HC05C4ACFB Motorola / Freescale Semiconductor, CM68HC05C4ACFB Datasheet - Page 67

• Manufacturer Part Number: CM68HC05C4ACFB
• Description: Microcontroller
• Manufacturer: Motorola / Freescale Semiconductor

9.5.1.3 Break Characters
9.5.1.4 Idle Characters
9.5.1.5 Transmitter Interrupts
MC68HC05C4A
MOTOROLA
—
Rev. 4.0
Writing a logic 1 to the SBK bit in SCCR2 loads the shift register with a
break character. A break character contains all logic 0s and has no start
and stop bits. Break character length depends on the M bit in SCCR1.
As long as SBK is at logic 1, transmitter logic continuously loads break
characters into the shift register. After software clears the SBK bit, the
shift register finishes transmitting the last break character and then
transmits at least one logic 1. The automatic logic 1 at the end of a break
character is to guarantee the recognition of the start bit of the next
character.
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 in 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.
Two sources can generate SCI transmitter interrupt requests:
1. Transmit Data Register Empty (TDRE) — The TDRE bit in the
2. Transmission Complete (TC) — The TC bit in the SCSR indicates
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.
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.
Serial Communications Interface (SCI)
Serial Communications Interface (SCI)
General Release Specification
SCI Operation
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