
Rev.2.00
Aug 28, 2006
page 139 of 148
7641 Group
REJ09B0336-0200
APPLICATION
2.12 Clock generating circuit
Item
Oscillation
CPU
Internal clock
φ
I/O ports
Timer
UART
DMAC
Serial I/O
USB
RAM
SFR
CPU registers
State in Stop mode
Stopped.
Stopped at “H” level.
Retains the state at the STP instruction execution.
When using internal count source: Stopped.
When using external count source: Operating.
Stopped.
When using internal syncronous clock: Stopped.
When using external syncronous clock: Operating.
Stopped.
Retained.
Retained (except for Timer 1, Timer 2).
Retained: Accumulator, Index register X, Index register Y, Stack
pointer, Program counter, Processor status register.
2.12.3 Stop mode
The Stop mode is set by executing the STP instruction. In Stop mode, the oscillation of both clocks (XIN–
XOUT, XCIN–XCOUT) stop and the internal clock
φ stops at the “H” level. The CPU stops and peripheral units
stop operating. As a result, power dissipation is reduced.
(1) State in Stop mode
Table 2.12.1 shows the state in Stop mode.
Table 2.12.1 State in Stop mode
(2) Release of Stop mode
The Stop mode is released by a reset input or by the occurrence of an interrupt request.
These interrupt sources can be used for restoration:
INT0, INT1
CNTR0, CNTR1
Timers X, Y using an external count source
Serial I/Os using an external clock
Key-on wake-up
USB function resume
However, when using any of these interrupt requests for restoration from Stop mode, in order to
enable the selected interrupt, set the following conditions before execution of STP instruction.
[Necessary register setting]
Timer 1 interrupt enable bit (b6 of ICONB) = “0” (interrupt disabled)
Timer 2 interrupt enable bit (b7 of ICONB) = “0” (interrupt disabled)
Timer 1 interrupt request bit (b6 of IREQB) = “0” (no interrupt request issued)
Timer 2 interrupt request bit (b7 of IREQB) = “0” (no interrupt request issued)
Interrupt request bit of interrupt source to be used for restoration = “0” (no interrupt request issued)
Interrupt enable bit of interrupt source to be used for restoration = “1” (interrupts enabled)
Interrupt disable flag I = “0” (interrupt enabled)
(3) Notes on STP instruction
Execution of STP instruction clears the timer 123 mode register (address 2916) except bit 4 to “0”.
When using fSYN as the internal system clock, switch to f(XIN) or f(XCIN) before execution of STP instruction.
Execution of STP instruction clears bit 7 of clock control register to “0” (f(XIN)/2).