Motorola MCF5282, MCF5281 user manual Clock and Reset Signals, Chip Configuration Signals

MCF5282 External Signals

14.2.3 Clock and Reset Signals

The clock and reset signals configure the MCF5282 and provide interface signals to the external system.

14.2.3.1 Reset In (RSTI)

Asserting RSTI causes the MCF5282 to enter reset exception processing. When RSTI is recognized the address bus, data bus, SIZ, R/W, AS, and TS are three-stated. RSTO is asserted automatically when RSTI is asserted.

14.2.3.2 Reset Out (RSTO)

After RSTI is asserted, the PLL temporarily loses its lock, during which time RSTO is asserted. When the PLL regains its lock, RSTO negates again. This signal can be used to reset external devices.

14.2.3.3 EXTAL

This input is driven by an external clock except when used as a connection to the external crystal when using the internal oscillator.

14.2.3.4 XTAL

This output is an internal oscillator connection to the external crystal.

14.2.3.5 Clock Output (CLKOUT)

The internal PLL generates CLKOUT. This output reflects the internal system clock.

14.2.4 Chip Configuration Signals

14.2.4.1 RCON

If the external RCON signal is asserted, then various chip functions, including the reset configuration pin functions after reset, are configured according to the levels driven onto the external data pins (see Section 30.6, “Functional Description”). The internal configuration signals are driven to reflect the levels on the external configuration pins to allow for module configuration.

14.2.4.2 CLKMOD[1:0]

The state of the CLKMOD[1:0] pins during reset determines the clock mode after reset.

14-22 MCF5282 User’s Manual MOTOROLA