MC68HC05JJ6 Datasheet, PDF(28/216 Page) Freescale Semiconductor, Inc – General Release Specification Microcontrollers

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MC68HC05JJ6 Datasheet, PDF (28/216 Pages) Freescale Semiconductor, Inc – General Release Specification Microcontrollers

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General Description

1.7.5 Internal Low-Power Oscillator

An internal low-power oscillator (LPO) is provided which has a nominal

frequency of 100 kHz. This oscillator can be selected via software in

place of the external oscillator which uses external components

connected to the OSC1 and OSC2 pins. When operating from this

internal LPO, the other oscillator can be powered down by software to

further conserve power.

All standard parts, whether 20 pin, 28 pin, RC option, or crystal, have the

nominal frequency of 100 kHz for the LPO. However, a 500-kHz

frequency LPO is available also. Either the 100-kHz or the 500-kHz LPO

is selected by the low-power oscillator mask option.

1.8 RESET Pin

The RESET pin can be used as an input to reset the MCU to a known

startup state by pulling it to the low state. It also functions as an output

to indicate that an internal COP watchdog, illegal address, or low-voltage

reset has occurred. The RESET pin contains a pullup device to allow the

pin to be left disconnected without an external pullup resistor. The

RESET pin also contains a steering diode that, when the power is

removed, will discharge to VDD any charge left on an external capacitor

connected between the RESET pin and VSS. The RESET pin also

contains an internal Schmitt trigger to improve its noise immunity as an

input.

1.9 IRQ Pin

The IRQ input pin drives the asynchronous IRQ interrupt function of the

CPU. Using a mask option, the IRQ interrupt function uses either

negative edge-sensitive triggering or both negative edge-sensitive and

low level-sensitive triggering. If level-sensitive triggering is selected, the

IRQ pin requires an external resistor to VDD for âwired-ORâ operation. If

the IRQ pin is not used, it must be tied to the VDD supply. The IRQ pin

contains an internal Schmitt trigger as part of its input to improve noise

immunity. The voltage on this pin may affect the mode of operation if the

General Release Specification

MC68HC05JJ6/MC68HC05JP6 â Rev. 3.2

General Description

Freescale Semiconductor

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