MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 252



Manufacturer Part Number
Advance Information
FREESCALE [Freescale Semiconductor, Inc]
Serial Communications Interface (SCI)
17.4.5 Break Characters
Advance Information
Writing a logic 1 to the send break bit, SBK (SCC2), loads the transmit
shift register with a break character. A break character contains all logic
0s and has no start, stop, or parity bit. Break character length depends
on the M bit (SCC1). As long as SBK is at logic 1, transmitter logic
continuously loads break characters into the transmit 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 guarantees the
recognition of the start bit of the next character.
The SCI recognizes a break character when a start bit is followed by
eight or nine logic 0 data bits and a logic 0 where the stop bit should be.
Receiving a break character has these effects on SCI registers:
Sets the framing error bit (FE) in SCS1
Sets the SCI receiver full bit (SCRF) in SCS1
Clears the SCI data register (SCDR)
Clears the R8 bit in SCC3
Sets the break flag bit (BKF) in SCS2
May set the overrun (OR), noise flag (NF), parity error (PE), or
reception in progress flag (RPF) bits
Serial Communications Interface (SCI)
Rev. 4.0

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