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Reduced Power Modes
In order to wake the device using a programmable interrupt, the interrupt mask
register must have the respective bit set to enable interrupt service (see Section 2.7, Interrupt Logic). In some cases, the ARM bit must also be set, in order
for the interrupts to be visible during sleep Table 2–3.
After the C614 wakes from sleep, the program counter assumes a specific
location, resuming normal operation of the device. Normally, the destination
of the program on wake-up is the interrupt service routine associated with the
interrupt which initiated the wake-up. The start of the interrupt service routine
is defined by the program location stored in the respective interrupt vector (see
Section 2.6.3, Interrupt Vectors). This wake-up response requires that the
global interrupt enable is set before going to sleep (use the INTE instruction).
If the global interrupt enable is CLEAR before going to sleep, then the
programmed interrupt can still wake the device, provided that the respective
IMR and ARM bits are set as in Table 2–5 Instead of waking to the interrupt
service routine, however, the program counter assumes the location
immediately following the IDLE instruction which initiated the sleep. This type
of wake-up response may be useful for putting the C614 into a hold sleep;
whereby, any number of programmable interrupts can wake the device, yet
they all return the program to the very same location. In order to accomplish
this, each of the necessary interrupts should be enabled in the IMR. The global
interrupt enable, however, is cleared using the INTD instruction. Table 2–6 lists
the various possible destinations of the program counter on wake-up, provided
that the wake-up is bound to occur under the given conditions.
Table 2–6. Destination of Program Counter on Wake-Up Under Various Conditions
State of Interrupt Controls
before IDLE Instruction
Assuming Wake-Up can occur…
Destination of Program Counter after Wake-Up
• Global interrupt enable is SET
• Respective IMR bit is SET
Program counter goes to the location stored in the interrupt vector
associated with the waking Interrupt.
• Global interrupt enable is CLEAR
• Respective IMR bit is SET
Program counter goes to the next instruction immediately following
the IDLE which initiated sleep.
• Global interrupt enable is SET
• Respective IMR bit is CLEAR
Wake-up cannot occur from the programmed Interrupt under these
conditions.
If RESET low-to-high occurs, then program goes to the location
stored in the RESET interrupt vector.
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