MC68LC302 Datasheet, PDF (31/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

Configuration, Clocking, Low Power Modes, and Internal Memory Map
PB9Ev and PB9En are both set to one. PB9Ev is cleared by writing a one (writing a zero
has no effect).
In modem applications RI should be connected to the PB9 pin.
PB10Ev—PB10 Event
This bit will be set to one when there is a high to low transition on the PB10 pin. When
PB10En is set and PB10Ev is set, the IMP will wake-up from the selected power down
state, and the PB10 Interrupt will be generated. The IMP cannot enter the power-down
mode when PB10Ev and PB10En are both set to one. PB10Ev is cleared by writing a one
(writing a zero has no effect).
In modem applications the DTE TxD line may be connected to the PB10 pin.
PITEv—PIT Event
This bit will be set to one when there is a time-out on the periodic interrupt timer (PIT).
When PITEn bit is set and a time-out occurs (PITEv is set), the IMP will wake-up from the
selected power down, and a PIT Interrupt will be generated. The IMP cannot enter the
power-down mode if PITEv and PITEn are both set to one. PITEv is cleared by writing a
one (writing a zero has no effect).
PB9En—PB9 Enable
This bit, when set, enables the IMP to wake up from power down mode and generate an
interrupt when the PB9 Event bit becomes set.
PB10En—PB10 Enable
This bit, when set, enables the IMP to wake up from power down mode and generate an
interrupt when the PB10 Event bit becomes set.
PITEn—PIT Enable
This bit, when set, enables the IMP to wake up from power down mode and generate an
interrupt when the PIT event bit becomes set, see 3.7.4 Periodic Interrupt Timer (PIT).
2.4.4.3 FAST WAKE-UP
In a system clocked with a 32-kHz oscillator, the wake-up recovery time from doze and stop
modes may be too long for some applications. In order to shorten this time, an internal ring
oscillator (called Ringo) can clock the chip (the term “real clock” in the following discussion
refers to the clock whose source is the external oscillator or crystal; the PLL can be either
enabled or disabled). One reason for using the fast wake-up is:
• To allow logic to operate in the time frame between the wake-up command and the ac-
tual real clock recovery (from the external crystal or oscillator).
NOTE
If the SCCs use the internal clock, or if they use external clock
and the Ringo/external frequency ratio does not comply with the
1 / 2.5 maximum ration specification, then they cannot be en-
abled until the real clock has resumed operation.
2-18
MC68LC302 REFERENCE MANUAL
MOTOROLA