MC68HC908GZ8 Datasheet, PDF (234/344 Pages) Motorola, Inc – Microcontrollers

Enhanced Serial Communications Interface (ESCI) Module
19.5.2 Stop Mode
The ESCI module is inactive in stop mode. The STOP instruction does not affect
ESCI register states. ESCI module operation resumes after the MCU exits stop
mode.
Because the internal clock is inactive during stop mode, entering stop mode during
an ESCI transmission or reception results in invalid data.
19.6 ESCI During Break Module Interrupts
The BCFE bit in the break flag control register (SBFCR) enables software to clear
status bits during the break state. See Section 6. Break Module (BRK).
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 two-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.
19.7 I/O Signals
Port E shares two of its pins with the ESCI module. The two ESCI I/O pins are:
• PTE0/TxD — transmit data
• PTE1/RxD — receive data
19.7.1 PTE0/TxD (Transmit Data)
The PTE0/TxD pin is the serial data output from the ESCI transmitter. The ESCI
shares the PTE0/TxD pin with port E. When the ESCI is enabled, the PTE0/TxD
pin is an output regardless of the state of the DDRE0 bit in data direction register
E (DDRE).
19.7.2 PTE1/RxD (Receive Data)
The PTE1/RxD pin is the serial data input to the ESCI receiver. The ESCI shares
the PTE1/RxD pin with port E. When the ESCI 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
234
Enhanced Serial Communications Interface (ESCI) Module
MC68HC908GZ8
Freescale Semiconductor