MC68HC08AS32A Datasheet, PDF (186/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Serial Communications Interface (SCI)
13.5.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction. The STOP
instruction does not affect SCI register states. SCI module operation resumes after
an external interrupt.
Because the internal clock is inactive during stop mode, entering stop mode during
an SCI transmission or reception results in invalid data.
13.6 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules
can be cleared during the break state. The BCFE bit in the SIM break flag control
register (SBFCR) enables software to clear status bits during the break state.
To allow software to clear status bits during a break interrupt, write a logic 1 to the
BCFE bit. If a status bit is cleared during the break state, it remains cleared when
the MCU exits the break state.
To protect status bits during the break state, write a logic 0 to the BCFE bit. With
BCFE at logic 0 (its default state), software can read and write I/O registers during
the break state without affecting status bits. Some status bits have a 2-step
read/write clearing procedure. If software does the first step on such a bit before
the break, the bit cannot change during the break state as long as BCFE is at
logic 0. After the break, doing the second step clears the status bit.
13.7 I/O Signals
Port E shares two of its pins with the SCI module. The two SCI I/O pins are:
• PTE0/TxD — Transmit data
• PTE1/RxD — Receive data
13.7.1 PTE0/TxD (Transmit Data)
The PTE0/TxD pin is the serial data output from the SCI transmitter. The SCI
shares the PTE0/TxD pin with port E. When the SCI is enabled, the PTE0/TxD pin
is an output regardless of the state of the DDRE2 bit in data direction register E
(DDRE).
13.7.2 PTE1/RxD (Receive Data)
The PTE1/RxD pin is the serial data input to the SCI receiver. The SCI shares the
PTE1/RxD pin with port E. When the SCI is enabled, the PTE1/RxD pin is an input
regardless of the state of the DDRE1 bit in data direction register E (DDRE).
Data Sheet
186
Serial Communications Interface (SCI)
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MC68HC08AS32A — Rev. 1
MOTOROLA