mc68hc912d60c Freescale Semiconductor, Inc, mc68hc912d60c Datasheet - Page 45

• Manufacturer Part Number: mc68hc912d60c
• Description: Hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

3.5.1.2 External Oscillator Connections
3.5.2 E-Clock Output (ECLK)
3.5.3 Reset (RESET)
MC68HC912D60A — Rev. 3.1
Freescale Semiconductor
NOTE:
When selecting a crystal, it is recommended to use one with the lowest
possible frequency in order to minimise EMC emissions.
XTAL is the crystal output. The XTAL pin must be left unterminated when
an external CMOS compatible clock input is connected to the EXTAL
pin. The XTAL output is normally intended to drive only a crystal. The
XTAL output can be buffered with a high-impedance buffer to drive the
EXTAL input of another device.
ECLK is the output connection for the internal bus clock and is used to
demultiplex the address and data and is used as a timing reference.
ECLK frequency is equal to 1/2 the crystal frequency out of reset. The
ECLK output is turned off in single chip user mode to reduce the effects
of RFI. It can be turned on if necessary. In single-chip special mode, the
ECLK is turned ON at reset and can be turned OFF. In special peripheral
mode the ECLK is an input to the MCU. All clocks, including the ECLK,
are halted when the MCU is in STOP mode. It is possible to configure
the MCU to interface to slow external memory. ECLK can be stretched
for such accesses.
An active low bidirectional control signal, RESET, acts as an input to
initialize the MCU to a known start-up state. It also acts as an open-drain
Pinout and Signal Descriptions
Figure 3-6. External Oscillator Connections
MCU
EXTAL
XTAL
NC
EXTERNAL OSCILLATOR
Pinout and Signal Descriptions
CMOS-COMPATIBLE
2 x E
Signal Descriptions
Technical Data
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