GMS30C7201 Datasheet, PDF (63/352 Pages) Hynix Semiconductor – 60MHz operation frequency Low power consumption

PMU & PLL
Wake-up Debounce and Interrupt
The Wake-up events are debounced as follows:
Each of the event signals which are liable to noise (nRESET, RTC, nPMWAKEUP, and
Modem Ring Indicator, Power Adapter Condition) is re-timed to a 250Hz clock derived
from the low power (4kHz) clock. After filtering to a quarter of 250 Hz, each event has an
associated ‘sticky’ register bit. nPMWAKEUP is an external input, which may be typically
connected to an “ON” key.
A ‘sticky’ bit is a register bit that is set by the incoming event, but is only reset by the CPU.
Thus should a PLL drop out of lock momentarily (for example) the CPU will be informed of the
event, even if the PLL has regained lock by the time the CPU can read its associated register bit.
The nPMWAKEUP, Modem, Real Time Clock and Power Adapter condition inputs are
combined to form the PMU Interrupt. Each of these three interrupt sources may be individually
enabled.
To make use of the nPMWAKEUP Interrupt, (for example) controlling software will need to
complete the following tasks:
• Enable the nPMWAKEUP interrupt bit, by writing 0 to bit 9 of the ResetStatus
register.
• Once an interrupt has occurred, read the RESET / Status register to identify the
source(s) of interrupt. In the case of a nPMWAKEUP event, the register will return
0x10.
• Clear the appropriate ‘sticky’ bit by writing a 1 to the appropriate location (in the
nPMWAKEUP case, this will be 0x10.).
PORTA Wake-up Sequence
The PORTA interrupt is OR gated with nPMWAKEUP to support additional wake up sources.
Each PORTA input signal can be used as a wake up source, they are enabled using the Interrupt
MASK Register. After wake up, s/w should program the PORTA Interrupt MASK Register and/
or the PMU ResetStatus Register.
One possible application is to use the nDCD signal, from the a UART interface, as a wake up
source, by connecting nDCD to a PORTA input. In Deep Sleep mode, nDCD can wake up the
system by generating a PORTA interrupt request to the PMU block. The PMU state machine
then returns the system to the operational mode.
GMS30C7201 Data Sheet
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