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Chapter 8
Clock Generator
Preliminary User’s Manual U14913EE1V0UM00
8.5.5 WATCH mode
In this mode f
CPU
clock is stopped while the oscillator continue to operate to achieve low power, though
only oscillator & Watch/watchdog timer continue to operate.
This mode compensates the HALT modes concerning the oscillator stabilization time and power con-
sumption. Only for the Flash memory an additional stabilization time is required.
This mode is entered by configuring 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 8-9: Operating States in WATCH Mode
Watch mode release:
The WATCH mode can be released by a non-maskable interrupt request, an unmasked maskable
interrupt request, or RESET signal input.
(1)
Release by interrupt request:
The WATCH mode is released unconditionally by an unmasked maskable interrupt request regard-
less of its priority level. After 1 ms 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 inter-
rupt request is generated, the interrupt request is acknowledged along with the WATCH mode
release.
Items
Operation
Clock generator
Operating
Internal system clock
Stopped
WT, WDT, LCD clock
Operating
CPU
Stopped
I/O line
Unchanged
Peripheral function
Stops exclude watch/watchdog, LCD
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, UWR/LWR, CS[4:2]
H
CLKOUT
L
WAIT
Input value is not sampled
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