ST & T UPSD3212C - Manual (Page 39)

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uPSD3212A, uPSD3212C, uPSD3212CV
POWER-SAVING MODE
Two software selectable modes of reduced power
consumption are implemented (see Table
25 ).
Idle Mode
The following Functions are Switched Off.
–
CPU (Halted)
The following Function Remain Active During Idle
Mode.
–
External Interrupts
– Timer 0, Timer 1, Timer 2
– PWM Units
– USART
– 8-bit ADC
– I
2
C Interface
– USB Interface
Note: Interrupt or RESET terminates the Idle
Mode.
Power-Down Mode
–
System Clock Halted
– LVD Logic Remains Active
– SRAM contents remains unchanged
– The SFRs retain their value until a RESET is
asserted
Note: The only way to exit Power-down Mode is a
RESET.
Power Control Register
The Idle and Power-down Modes are activated by
software via the PCON register (see Tables
26
and Table 27., page 40 ).
Idle Mode
The instruction that sets PCON.0 is the last in-
struction executed in the normal operating mode
before Idle Mode is activated. Once in the Idle
Mode, the CPU status is preserved in its entirety:
Stack pointer, Program counter, Program status
word, Accumulator, RAM and All other registers
maintain their data during Idle Mode.
There are three ways to terminate the Idle Mode.
–
Activation of any enabled interrupt will cause
PCON.0 to be cleared by hardware
terminating Idle mode. The interrupt is
serviced, and following return from interrupt
instruction RETI, the next instruction to be
executed will be the one which follows the
instruction that wrote a logic '1' to PCON.0.
– External hardware reset: the hardware reset is
required to be active for two machine cycle to
complete the RESET operation.
– Internal reset: the microcontroller restarts after
3 machine cycles in all cases.
Power-Down Mode
Table 25. Power-Saving Mode Power Consumption
Table 26. Pin Status During Idle and Power-down Mode
Mode Addr/Data Ports1,3,4 PWM I 2 C USB
Idle Maintain Data Maintain Data Active Active Active
Power-down Maintain Data Maintain Data Disable Disable Disable
SFR
Addr
Reg
Name
Bit Register Name
Reset
Value
Comments
7 6 5 4 3 2 1 0
87 PCON SMOD SMOD1 LVREN ADSFINT RCLK1 TCLK1 PD IDLE 00 Power Ctrl