HC705JB2GRSSLASHH datasheet(18/128 Pages) NXP

18 / 128 page

GENERAL RELEASE SPECIFICATION

August 28, 1998

GENERAL DESCRIPTION

MC68HC705JB2

1-6

REV 1.1

components should be mounted as close as possible to the pins for start-up

stabilization and to minimize output distortion. An internal start-up resistor of 2M

Ω

(typical) is provided between OSC1 and OSC2 for the ceramic resonator type

oscillator.

1.4.2.3

External Clock

An external clock from another CMOS-compatible device can be connected to the

OSC1 input, with the OSC2 input not connected, as shown in Figure 1-3(b).

1.4.3 RESET

This is an I/O pin. This pin can be used as an input to reset the MCU to a known

start-up state by pulling it to the low state. The RESET pin contains a steering

diode to discharge any voltage on the pin to VDD, when the power is removed. An

internal pull-up is also connected between this pin and VDD. The RESET pin

contains an internal Schmitt trigger to improve its noise immunity as an input. This

pin is an output pin if LVR triggers an internal reset.

1.4.4 IRQ/VPP

This input pin drives the asynchronous IRQ interrupt function of the CPU. The IRQ

interrupt function has a mask option to provide either only negative edge-sensitive

triggering or both negative edge-sensitive and low level-sensitive triggering. If the

option is selected to include level-sensitive triggering, the IRQ input requires an

external resistor to VDD for "wired-OR" operation, if desired. The IRQ pin contains

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

NOTE

Each of the PA0 thru PA3 I/O pins may be connected as an OR

function with the IRQ interrupt function by a mask option. This

capability allows keyboard scan applications where the transitions or

levels on the I/O pins will behave the same as the IRQ pin, except

for the inverted phase. The edge or level sensitivity selected by a

separate mask option for the IRQ pin also applies to the I/O pins

OR’ed to create the IRQ signal.

In Bootloader mode, this pin (VPP) is used to supply the required programming

voltage to the EPROM array.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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