4524_M Datasheet, PDF (244/310 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 720 FAMILY / 4500 SERIES

4524 Group
APPLICATION
2.9 Power down
Table 2.9.2 Return source and return condition
Return source
Return condition
Remarks
Ports P00–P03 Return by an external “L” level The key-on wakeup function can be selected by one
Ports P10–P13 input.
port unit. Set the port using the key-on wakeup function
to “H” level before going into the power down state.
INT0 pin
Return by an external “H” level Select the return level (“L” level or “H” level) with register
INT1 pin
or “L” level input, or rising edge I1 (I2) and return condition (return by level or edge)
(“L”→“H”) or falling edge with register K2 according to the external state before
(“H”→“L”).
going into the power down state.
When the return signal is input,
the interrupt request flag (EXF0,
EXF1) is not set to “1”.
Timer 5 interrupt _{Return by timer 5 underflow or Clear T5F to “0” with the SNZT5 instruction before}
request flag (T5F) _{by setting T5F to “1”.}
system goes into the power down state.
It can be used in the clock When system goes into the power down state while
operating mode.
T5F is “1”, system returns from the state immediately
because it is recognized as return condition.
(3) Start condition identification
When system returns from both power down mode and reset, program is started from address 0 in
page 0.
The start condition (warm start or cold start) can be identified by examining the state of the power
down flag (P) with the SNZP instruction.
The warm start condition (Timer 5 or external wakeup signal) can be identified by examining the state
of T5F flag with the SNZT5 instruction.
Table 2.9.3 Start condition identification
Start condition
Warm start External wakeup signal input
Timer 5 underflow
Cold start Reset pulse input to RESET pin
(Reset)
Reset by watchdog timer
Reset by voltage drop detection circuit
P flag
1
1
0
Timer 5 interrupt request flag
0
1
0
Program start
P = “1”
Yes
?
No
Cold start
Return from
timer 5 underflow
Warm start
Yes
T5F = “1”
?
No
Return from
external wakeup signal
Fig. 2.9.2 Start condition identified example
Rev.2.00 Aug, 06 2004
REJ09B0107-0200Z
2-80