Motorola MC68340 manual Instrumentation and Emulation Signals

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

2.10.2 Crystal Oscillator (EXTAL, XTAL)

These two pins are the connections for an external crystal to the internal oscillator circuit. If an external oscillator is used, it should be connected to EXTAL, with XTAL left open.

2.10.3 External Filter Capacitor (XFC)

This pin is used to add an external capacitor to the filter circuit of the phase-locked loop. The capacitor should be connected between XFC and VCCSYN.

2.10.4 Clock Mode Select (MODCK)

This pin selects the source of the internal system clock during reset. After reset, it can be programmed to be port B parallel I/O.

MODCK

The state of this active-high input signal during reset selects the source of the internal system clock. If MODCK is high during reset, the internal voltage-controlled oscillator (VCO) furnishes the system clock in crystal mode. If MODCK is low during reset, an external clock source at the EXTAL pin furnishes the system clock output in external clock mode.

Port B0

This pin can be used as a port B parallel I/O.

2.11 INSTRUMENTATION AND EMULATION SIGNALS

These signals are used for test or software debugging. See Section 5 CPU32 for more information on these signals and background debug mode.

2.11.1 Instruction Fetch (IFETCH)

This pin functions as IFETCH in normal operation and as DSI in background debug mode.

IFETCH

This active-low output signal indicates when the CPU32 is performing an instruction word prefetch and when the instruction pipeline has been flushed.

DSI

This development serial input signal helps to provide serial communications for background debug mode.

2.11.2 Instruction Pipe (IPIPE)

This pin functions as IPIPE in normal operation and as DSO in background debug mode.

MOTOROLAMC68340 USER’S MANUAL2- 9

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