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CHAPTER 20 STANDBY FUNCTION
20.2.2 STOP mode
(1) Setting and operation status of STOP mode
The STOP mode is set by executing the STOP instruction. This mode can be set only when the system operates
on the main system clock.
Cautions 1. When the STOP mode is set, X2 pin is internally pulled up circuited to V
DD
to suppress
the current leakage of the crystal oscillation circuit block. Therefore, do not use the STOP
mode in a system where the external clock is used as the main system clock.
2. Because the standby mode can be released by an interrupt request signal, the standby
mode is released as soon as it is set if there is an interrupt source whose interrupt request
flag is set and interrupt mask flag is reset. When the STOP mode is set, therefore, the
HALT mode is set immediately after the STOP instruction has been executed, the wait
times set by the oscillation stabilization time select register (OSTS) elapses, and then
an operation mode is set.
The following table shows the operation status in the STOP mode.
Table 20-3. Operation Status in STOP Mode
Item
Clock generation circuit
Only main system clock stops oscillation
CPU
Stops operation
Output port (output latch)
Retains previous status immediately before STOP instruction execution
16-bit timer/event counter
Stops operation
8-bit timer/event counter
Operable only when TI1 or TI2 is selected as count clock
Watchdog timer
Stops operation
A/D converter
Watch timer
Operable only when f
XT
is selected
as count clock
Stops operation
Operable only when external input clock is selected as serial clock
Stops operation
INTP0
Cannot operate
INTP1-INTP3
Operable
AD0-AD7
High impedance
A8-A15
Retains previous status immediately before STOP instruction execution
ASTB
Low level
WR, RD
High level
WAIT
High impedance
When Subsystem Clock is Used
When Subsystem Clock is Not Used
Serial
interface
Other than
automatic
transmit/receive
function
Setting of STOP
Mode
Automatic
transmit/receive
function
External
interrupt
Externally
extended
bus line