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DSP56853/854/855/857/858 User’s Manual
MOTOROLA
Preliminary
Functional Description
14
14.4.3 Stop Mode
During Stop Mode the TOD module will continue to operate normally. The TOD
interrupts will still activate and can wake the processor up for TOD related processing.
14.4.4 General Information
The TOD alarms sub block is used to generate TOD IRQ signals. The TOD alarm registers
TODSAL, TODMAL, TODHAL, and TODDAL, along with TOD control/status register
(TODCS), are implemented in this sub block.
TOD generates two interrupt signals:
1. TOD Alarm Interrupt
2. TOD Second Interrupt
Both interrupt signals can wake up the device from its stop mode.
14.4.5 Alarm Interrupt Flag and Outputs
The alarm interrupt feature provides a flexible means of detecting events based on time of
day. The TOD module contains alarm registers for seconds, minutes, hours, and days. The
control and status register contains individual enables for each of these registers (TODSA,
TODMA, TODHA, TODDA) as well as an overall Alarm Interrupt Enable (TODAEN).
An alarm interrupt triggers during the time of day counting process. This interrupt occurs
when at least one of the alarm enables is set and the TODAEN is set.
All alarm registers can be enabled to generate an alarm at a designated time. All enabled
alarm registers must match the corresponding time registers before the TOD alarm
interrupt IRQ is generated. For example, if the minutes and hour alarms are enabled, then
both the minutes and hours registers must match the respective alarm registers before the
IRQ will occur.
The alarm interrupt triggers one TOD input clock period after the TOD_CLK edge,
advancing the time of day counters to their activation value. To minimize latency, it is
preferable to generate a faster TOD input clock and use a correspondingly higher value in
the TOD module’s clock scaler register. The alarm interrupt will not trigger until TODEN
is set to one and all enabled alarm registers match the time of day counters. The interrupt
will function in the Stop mode; however, the TOD module must be configured and
enabled prior to entering the Stop mode.
Every time the alarm interrupt triggers the TOD Alarm interrupt occurred flag (TODAL)
in the control status register is set. The TODAL is cleared by writing a zero to it while it