3804H_M Datasheet, PDF (275/387 Pages) Renesas Technology Corp – 8-BIT CISC SINGLE-CHIP MICROCOMPUTER 740 FAMILY / 38000 SERIES

3804 Group (Spec.H)
APPLICATION
2.12 Standby function
sRestoration by interrupt request
The occurrence of an interrupt request in the stop mode releases the stop mode. As a result,
oscillation is resumed. The interrupts available for restoration are:
•INT0–INT4
•CNTR0, CNTR1, CNTR2
•Serial I/O (1, 2, 3) using an external clock
•Timer X, Y, Z using an external event count
•SCL/SDA
However, when using any of these interrupt requests for restoration from the stop mode, in order to
enable the selected interrupt, you must execute the STP instruction after setting the following conditions.
[Necessary register setting]
➀ Interrupt disable flag I = “0” (interrupt enabled)
➁ Timer 1 interrupt enable bit = “0” (interrupt disabled)
➂ Interrupt request bit of interrupt source to be used for restoration = “0” (no interrupt request
issued)
➃ Interrupt enable bit of interrupt source to be used for restoration = “1” (interrupts enabled)
For more details concerning interrupts, refer to “2.2 Interrupts”.
Oscillation is unstable when restarted. For this reason, time for stabilizing of oscillation (oscillation
stabilizing time) is required. For restoration by an interrupt request, waiting time prior to supplying
internal clock φ to the CPU is automatically generated^✽2 by Prescaler 12 and Timer 1^✽1. This waiting
time is reserved as the oscillation stabilizing time on the system clock side. The supply of internal
clock φ to the CPU is started at the Timer 1 underflow.
Figure 2.12.2 shows an execution sequence example at restoration by the occurrence of an INT0
interrupt request.
✽1: If the STP instruction is executed when the oscillation stabilizing time set after STP instruction
released bit is “0”, “FF16” and “0116” are automatically set in the Prescaler 12 counter/latch and
Timer 1 counter/latch, respectively. When the oscillation stabilizing time set after STP instruction
released bit is “1”, nothing is automatically set to either Prescaler 12 or Timer 1. For this reason,
any suitable value can be set to Prescaler 12 and Timer 1 for the oscillation stabilizing time.
✽2: Immediately after the oscillation is started, the count source is supplied to the prescaler 12 so
that a count operation is started.
Rev.1.00 Jan 14, 2005
REJ09B0212-0100Z
2-151