R8C/1A Group, R8C/1B Group
10. Clock Generation Circuit
Rev.1.30
Dec 08, 2006
Page 71 of 315
REJ09B0252-0130
Figure 10.8 shows the Time from Wait Mode to Interrupt Routine Execution.
To use a peripheral function interrupt to exit wait mode, set up the following before executing the WAIT
instruction.
(1) Set the interrupt priority level in bits ILVL2 to ILVL0 in the interrupt control registers of the peripheral
function interrupts to be used for exiting wait mode. Set bits ILVL2 to ILVL0 of the peripheral function
interrupts that are not to be used for exiting wait mode to 000b (interrupt disabled).
(2) Set the I flag to 1.
(3) Operate the peripheral function to be used for exiting wait mode.
When exiting by a peripheral function interrupt, the interrupt sequence is executed when an interrupt request is
generated and the CPU clock supply is started.
The CPU clock, when exiting wait mode by a peripheral function interrupt, is the same clock as the CPU clock
when the WAIT instruction is executed.
Figure 10.8
Time from Wait Mode to Interrupt Routine Execution
0
(flash memory operates)
1
(flash memory stops)
Period of CPU clock
×
20 cycles
Same as above
Following total time is the
time from wait mode until
an interrupt routine is
executed.
Wait mode
Flash memory
activation sequence
T1
CPU clock restart sequence
T2
Interrupt sequence
T3
Interrupt request generated
FMSTP Bit
Time for Interrupt
Sequence (T3)
Remarks
FMR0 Register
Period of system clock
×
12 30
µ
s (max.)
Period of system clock
×
12 cycles
Time until Flash Memory
is Activated (T1)
Period of CPU clock
×
6 cycles
Same as above
Time until CPU Clock
is Supplied (T2)