HC705RC17GRSSLASHD datasheet(20/126 Pages) NXP

20 / 126 page

General Description

General Release Specification

MC68HC705RC17 — Rev. 2.0

General Description

1.5.2 IRQ/VPP (Maskable Interrupt Request)

This pin supplies the EPROM with the required programming voltage. In

addition, this pin serves as the input for external interrupts. Triggering

sensitivity is programmable using MOR1. The options are:

1. Negative edge-sensitive triggering only

2. Both negative edge-sensitive and level-sensitive triggering

The MCU completes the current instruction before it responds to the

interrupt request. When IRQ goes low for at least one t

ILIH, a logic 1 is

latched internally to signify that an interrupt has been requested. When

the MCU completes its current instruction, the interrupt latch is tested. If

the interrupt latch contains a logic 1 and the interrupt mask bit (I bit) in

the condition code register is clear, the MCU then begins the interrupt

sequence.

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

requires an external resistor to V

DD for wired-OR operation.

The IRQ pin contains an internal Schmitt trigger as part of its input to

improve noise immunity.

Refer to Section 4. Interrupts for more detail.

1.5.3 OSC1 and OSC2

These pins provide control input for an on-chip clock oscillator circuit. A

crystal, a ceramic resonator, or an external signal connects to these pins

to provide a system clock. The oscillator frequency is two times the

internal bus rate.

Figure 1-4 shows the recommended circuit when using a crystal. The

crystal and components should be mounted as close as possible to the

input pins to minimize output distortion and startup stabilization time.

A ceramic resonator may be used in place of the crystal in cost-sensitive

applications. Figure 1-4 (a) shows the recommended circuit for using a

ceramic resonator. The manufacturer of the particular ceramic resonator

being considered should be consulted for specific information.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705RC17GRS/D Datasheet(PDF) 20 Page - NXP Semiconductors