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Chapter 9
Clock Generator
Preliminary User’s Manual U15839EE1V0UM00
9.4.6 WATCH mode
In this mode f
CPU
clock is stopped while the oscillator continue to operate to achieve low power, though
only oscillator & Watch timer / Watchdog timer continue to operate.
This mode compensates the HALT modes concerning the oscillator stabilization time and power con-
sumption.
As it is not necessary to secure the oscillation stabilization time, it is possible immediately to switch to
the normal operating mode in response to a release cause.
This mode is entered by configuration the PSM and PSC registers.
In the WATCH mode, program execution is stopped but the contents of all registers and internal RAM
prior to entering this mode are retained. On-chip other peripheral hardware operation is also stopped.
The state of the various hardware units in the WATCH mode is tabulated below.
Table 9-7:
Operating States in WATCH Mode
Watch mode release:
The WATCH mode can be released by a non-maskable interrupt request, an unmasked maska-
ble interrupt request, or RESET signal input.
(1)
Release by interrupt request:
The WATCH mode is released unconditionally by an unmasked maskable interrupt request
regardless of its priority level. After oscillator stabilization time has passed, CPU starts operation.
However, if the WATCH mode is entered during execution of an interrupt handler, the operation
differs on interrupt priority levels as follows:
(a) If an interrupt request less priorities than the currently serviced interrupt request is generated,
the WATCH mode is release but the interrupt is not acknowledged. The interrupt request itself
is retained.
(b) If an interrupt request (including a non-maskable one) priorities than the currently serviced
interrupt request is generated, the interrupt request is acknowledged along with the WATCH
mode release.
Items
Operation
Clock generator
Operating
SSCG/PLL
Stopped
Internal system clock
Stopped
WT, WDT clock
Operating
CPU
Stopped
I/O line
Unchanged
Peripheral function
Stops exclude Watch timer / Watchdog timer
TMC calibration input
Main Clock available
Internal data
Retains all internal data before entering WATCH mode,
such as CPU registers, status, data, and on-chip RAM.
D[15:0], A[23:0]
Hi-Z
RD, WR1/WR0, CS[0], CS[4:2]
H
CLKOUT
L
WAIT
Input value is not sampled
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