Intel 80C196NU ユーザーズマニュアル
12-8
8XC196NP, 80C196NU USER’S MANUAL
After completing these tasks, execute the IDLPD #2 instruction to enter powerdown mode.
NOTE
To prevent an accidental return to full power, hold the external interrupt pins
(EXTINTx) low while the device is in powerdown mode.
(EXTINTx) low while the device is in powerdown mode.
12.5.3 Exiting Powerdown Mode
The device will exit powerdown mode when either of the following events occurs:
•
a hardware reset is generated, or
•
a transition occurs on an external interrupt pin.
NOTE
It was previously documented that the method of exiting powerdown mode by
driving the RPD pin low was acceptable; however, we no longer recommend
this method as an option for exiting powerdown.
driving the RPD pin low was acceptable; however, we no longer recommend
this method as an option for exiting powerdown.
12.5.3.1
Generating a Hardware Reset
The device will exit powerdown if RESET# is asserted. If the phase-locked loop circuitry is en-
abled or if the design uses an external clock input signal rather than the on-chip oscillator,
RESET# must remain low for at least 16 state times. If the design uses the on-chip oscillator, then
RESET# must be held low until the oscillator and phase-locked loop circuitry have stabilized.
abled or if the design uses an external clock input signal rather than the on-chip oscillator,
RESET# must remain low for at least 16 state times. If the design uses the on-chip oscillator, then
RESET# must be held low until the oscillator and phase-locked loop circuitry have stabilized.
12.5.3.2
Asserting an External Interrupt Signal
The final way to exit powerdown mode is to assert an external interrupt signal (EXTINT3:0) for
at least one state time. Although EXTINT3:0 are normally sampled inputs, the powerdown cir-
cuitry uses them as level-sensitive inputs. The interrupts need not be enabled to bring the device
out of powerdown, but the pin must be configured as a special-function input (see “Bidirectional
Port Pin Configurations” on page 7-7). Figure 12-3 shows the power-up and powerdown se-
quence when using an external interrupt to exit powerdown.
at least one state time. Although EXTINT3:0 are normally sampled inputs, the powerdown cir-
cuitry uses them as level-sensitive inputs. The interrupts need not be enabled to bring the device
out of powerdown, but the pin must be configured as a special-function input (see “Bidirectional
Port Pin Configurations” on page 7-7). Figure 12-3 shows the power-up and powerdown se-
quence when using an external interrupt to exit powerdown.
When an external interrupt brings the device out of powerdown mode, the corresponding pending
bit is set in the interrupt pending register. If the interrupt is enabled, the device executes the in-
terrupt service routine, then fetches and executes the instruction following the IDLPD #2 instruc-
tion. If the interrupt is disabled (masked), the device fetches and executes the instruction
following the IDLPD #2 instruction and the pending bit remains set until the interrupt is serviced
or software clears the pending bit.
bit is set in the interrupt pending register. If the interrupt is enabled, the device executes the in-
terrupt service routine, then fetches and executes the instruction following the IDLPD #2 instruc-
tion. If the interrupt is disabled (masked), the device fetches and executes the instruction
following the IDLPD #2 instruction and the pending bit remains set until the interrupt is serviced
or software clears the pending bit.