MC68HC08AZ16 Datasheet, PDF (184/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Serial Communications Interface Module (SCI)
Functional description
Framing errors
If the data recovery logic does not detect a ’1’ where the stop bit
should be in an incoming character, it sets the framing error bit, FE,
in SCS1. The FE flag is set at the same time that the SCRF bit is set.
A break character that has no stop bit also sets the FE bit.
Receiver wake-up
So that the MCU can ignore transmissions intended only for other
receivers in multiple-receiver systems, the receiver can be put into a
standby state. Setting the receiver wake-up bit, RWU, in SCC2 puts
the receiver into a standby state during which receiver interrupts are
disabled.
Depending on the state of the WAKE bit in SCC1, either of two
conditions on the PTE1/RxD pin can bring the receiver out of the
standby state:
• Address mark — An address mark is a ’1’ in the most significant
bit position of a received character. When the WAKE bit is set, an
address mark wakes the receiver from the standby state by
clearing the RWU bit. The address mark also sets the SCI receiver
full bit, SCRF. Software can then compare the character
containing the address mark to the user-defined address of the
receiver. If they are the same, the receiver remains awake and
processes the characters that follow. If they are not the same,
software can set the RWU bit and put the receiver back into the
standby state.
• Idle input line condition — When the WAKE bit is clear, an idle
character on the PTE1/RxD pin wakes the receiver from the
standby state by clearing the RWU bit. The idle character that
wakes the receiver does not set the receiver idle bit, IDLE, or the
SCI receiver full bit, SCRF. The idle line type bit, ILTY, determines
whether the receiver begins counting ’1’s as idle character bits
after the start bit or after the stop bit.
NOTE: Clearing the WAKE bit after the PTE1/RxD pin has been idle may cause
the receiver to wake up immediately.
15-sci
MOTOROLA
Serial Communications Interface Module (SCI)
MC68HC08AZ32
183