MC68HC705C4ACB MOTOROLA [Motorola, Inc], MC68HC705C4ACB Datasheet - Page 122

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

Serial Communications Interface (SCI)
Technical Data
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After a complete character shifts into the receive shift register, the
data portion of the character is transferred to the SCDR, setting
the receive data register full (RDRF) flag. The RDRF flag can be
used to generate an interrupt.
Receiver Wakeup — So that the MCU can ignore transmissions
intended only for other receivers in multiple-receiver systems, the
MCU can be put into a standby state. Setting the receiver wakeup
enable (RWU) bit in SCI control register 2 (SCCR2) puts the MCU
into a standby state during which receiver interrupts are disabled.
Either of two conditions on the PD0/RDI pin can bring the MCU out
of the standby state:
– Idle input line condition — If the PD0/RDI pin is at logic 1 long
– Address mark — If a logic 1 occurs in the most significant bit
The state of the WAKE bit in SCCR1 determines which of the two
conditions wakes up the MCU.
Receiver Noise Immunity — The data recovery logic samples
each bit 16 times to identify and verify the start bit and to detect
noise. Any conflict between noise detection samples sets the
noise flag (NF) in the SCSR. The NF bit is set at the same time
that the RDRF bit is set.
Framing Errors — If the data recovery logic does not detect a logic
1 where the stop bit should be in an incoming character, it sets the
framing error (FE) bit in the SCSR. The FE bit is set at the same
time that the RDRF bit is set.
Receiver Interrupts — These sources can generate SCI receiver
interrupt requests:
– Receive Data Register Full (RDRF) — The RDRF bit in the
Serial Communications Interface (SCI)
enough for 10 or 11 logic 1s to shift into the receive shift
register, receiver interrupts are again enabled.
position of a received character, receiver interrupts are again
enabled.
SCSR indicates that the receive shift register has transferred a
character to the SCDR.
MC68HC705C4A • MC68HSC705C4A — Rev. 3.0
MOTOROLA