MO SEL VITELIC
MSU2051/U2031
Power Down Mode
General of above
It saves the RAM content, stops the clock generator
and disables every other blocks' function until the
coming hardware reset. To save even more power
consumption, user's software program can invoke this
mode. The SFRs and the on-chip data RAM retain
their values during this mode, but the porcessor stops
executing instructions. In Power-Down mode (PD=1)
the oscillator is frozen.
-An instruction that sets flag (PCON.1) causes that to
be the last instruction executed before going into the
Power Down Mode.
-In the Power Down Mode, the on-chip oscillator is
stopped.
User should fix the attention on using wake up from
port 2:
-The user should write the power down or idle mode
flag value to one RAM address before write PCON to
distinguish waking up from power down mode or idle
mode.
-After idle mode or power down mode wakes up, the
interrupt service routine will be executed first and then
executes PC+1 address if the IE register is enabled
before entering power down mode or idle mode. The
interrupt service routine will not be executed but CPU
executes PC+1 address program if disable IE register.
-After wake up power down or idle mode the IDF flag
will be set by hardware. The IDF flag be cleared at
the ISR execution time. If IE register is disable, the
IDF flag will not be cleared when power down or idle
mode wakes up.
With the clock frozen, all functions are stopped, but
the on-chip RAM and Special Function Registers are
held.
-Reset redefines all the SFRs, but does not change the
on-chip RAM.
-There are two ways to terminate the Power Down
Mode.
1) By hardware reset
All SFR and PC value will be cleared to reset value.
2) One of CLK, DATA, PORT 2.0-2.7 transition to low
(falling edge trigger)
After the program wakes up, the PC value will be
0023h (if enable IE register) and execute interrupt
service routine and then returns to PC+1 address after
the program wakes up.
-Care must be taken, however, to ensure that VCC is
not reduced before the Power Down Mode is invoked,
and that VCC is restored to its normal operating level
before the Power Down Mode is terminated.
-The hardware reset must be held active long enough
to allow the oscillator to restart and stabilize.
The state of pins during Idle and Power-Down Mode
Mode
Program
memory
ALE
#PSEN
Port 0
Port 1
Port 2
Port 3
Idle
Idle
Internal
External
Internal
External
1
1
0
0
1
1
0
0
Data
Float
Data
Float
Data
Data
Data
Data
Data
Data
Data
Data
Data
Address
Data
Power Down
Power Down
Data
Absolute Maximal Rating
* Note:
Symbol
Name
Rating
Unit
V
Remark
Operation beyond Absolute Maximal Rating
can adversely affect device reliability.
Vdd - Vss
DC supply Voltage
-0.5 ~ +5.0
-0.5 ~ +7.0
U20x1L
U20x1S,U20x1C
V
VIN
Input voltage
output voltage
Vss-0.3 ~ Vdd+0.3
Vss ~ Vdd
V
VOUT
T (Operating) Operating Temperature
T (Storage) Storage Temperature
0 ~ +70
°C
°C
-55 ~ +125
Rev. 1.0 February 1998
6
MOSEL [ MOSEL VITELIC, CORP ]
