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ACE1101MT8X View Datasheet(PDF) - Fairchild Semiconductor

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ACE1101MT8X Datasheet PDF : 33 Pages
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8.0 Multi-Input Wakeup Block
There are three memory-mapped registers associated with this
circuit: WKEDG (Wakeup Edge), WKEN (Wakeup Enable), and
WKPND (Wakeup Pending). Each register has eight bits, with the
six least significant bits corresponding to one of the input pins
shown in Figure 20. All three registers are initialized to zero with
a Reset.
The WKEDG register establishes the edge sensitivity for each of
the port input pins: either positive-going edges (0) or negative-
going edges (1).
The WKEN register enables (1) or disables (0) each of the port
pins for the Wakeup/Interrupt function. Any pin to be used for the
Wakeup/Interrupt function must also be configured as an input pin
in the PORTGC configuration register.
The WKPND register contains the pending flags corresponding to
each of the port pins (1 for wakeup/interrupt pending, 0 for
wakeup/interrupt not pending).
The T0CNTRL register is the Timer0 control register; however, bit
7 (WKINTEN) is used as the wakeup interrupt enable bit (see
Figure 18). By setting this bit the device can interrupt in the event
of a multi-input wakeup (if the global interrupt bit is set).
To use the Multi-Input Wakeup/Interrupt circuit, perform the steps
listed below. Performing the steps in the order shown will prevent
false triggering of a Wakeup/Interrupt condition. This same proce-
dure should be used following a Reset because the Wakeup
inputs will be set to high-impedence, resulting in unknown data on
the port inputs.
1. Clear the WKEN register.
2. Set the WKEN bit.
3. If necessary, write to the port configuration register to
change the desired port pins from outputs to inputs.
4. Write the WKEDG register to select the desired type of edge
sensitivity for each of the pins used.
5. Clear the WKPND register to cancel any pending bits.
6. Set the WKEN bits associated with the pins to be used, thus
enabling those pins for the Wakeup/Interrupt function.
Once the Multi-Input Wakeup/Interrupt function has been set up,
a transition sensed on any of the enabled pins will set the
corresponding bit in the WKPND register. This brings the device
out of the HALT mode (if in that mode), and also triggers a
maskable interrupt if that interrupt is enabled. The interrupt
service routine can read the WKPND register to determine which
pin triggered the interrupt.
The interrupt service routine or other software should clear the
pending bit. The device will not enter the HALT mode as long as
any WKPND pending bit is pending and enabled. The user has the
responsibility of clearing the pending flags before attempting to
enter the HALT mode.
After Reset, the WKEDG register is configured to select positive-
going edge sensitivity for all Wakeup inputs. If the user wishes to
change the edge sensitivity of a port pin, use the following
procedure to avoid false triggering of a Wakeup/Interrupt condi-
tion.
1. Disable the pin by clearing the associated bit in the WKEN
register.
2. Write to the associated bit of the WKEDG register selecting
the new edge sensitivity of the pin.
3. Clear the WKPND bit associated with the pin.
4. Re-enable the pin by setting the associated WKEN bit.
PORTG provides the user with eight fully selectable, edge sensi-
tive interrupts which are all vectored into the same service
subroutine.
The interrupt from PORTG shares logic with the wake up circuitry.
The WKEN register allows interrupts from PORTG to be individu-
ally enabled or disabled. The WKEDG register specifies the
trigger condition to be either a positive or a negative edge. The
WKPND register latches the pending trigger conditions.
Since PORTG is also used for exiting the device from the HALT
mode, the user can elect to exit the HALT mode either with or
without the interrupt enabled. If the user elects to disable the
interrupt, then the device restarts execution from the point at which
it was stopped (first instruction cycle of the instruction following the
enter HALT mode instruction). In the other case, the device
finishes the instruction which was being executed when the part
was stopped (the NOP instruction following the enter HALT mode
instruction), and then branches to the interrupt service routine.
The device then reverts to normal operation.
Figure 20: Multi-input Wakeup (MIWU) Block Diagram
Internal Data Bus
ACE1101 Rev. C.8
5
0
WKEN
G0
0
G5
5
WKEDG WKPND
26
WKOUTINT
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