MC68HC908GT16 Datasheet, PDF (268/412 Pages) Motorola, Inc – Microcontrollers

Enhanced Serial Communications Interface (ESCI)
18.5.3.6 Receiver Wakeup
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 wakeup 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 RxD pin can bring the receiver out of the standby state:
1. Address mark — An address mark is a logic 1 in the MSB 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 ESCI 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.
2. Idle input line condition — When the WAKE bit is clear, an idle
character on the 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 ESCI
receiver full bit, SCRF. The idle line type bit, ILTY, determines
whether the receiver begins counting logic 1s as idle character bits
after the start bit or after the stop bit.
NOTE: With the WAKE bit clear, setting the RWU bit after the RxD pin has been
idle will cause the receiver to wake up.
Technical Data
268
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
Enhanced Serial Communications Interface (ESCI) Module
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