COP8-REF-FL1 National Semiconductor, COP8-REF-FL1 Datasheet - Page 32

• Manufacturer Part Number: COP8-REF-FL1
• Description: KIT REF DESIGN FOR COP8SDR9
• Manufacturer: National Semiconductor
• Series: COP8™r
• Type: MCUr

Specifications of COP8-REF-FL1

• Design Resources: COP8 Flash Ref Design Flyer
• Contents: PCB, Control Interface, Documentation and 9V Battery
• For Use With/related Products: COP8SDR9
• Lead Free Status / RoHS Status: Not applicable / Not applicable

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7.0 Power Saving Features
7.3 MULTI-INPUT WAKE-UP
The Multi-Input Wake-up feature is used to return (wake-up)
the device from either the HALT or IDLE modes. Alternately
Multi-Input Wake-up/Interrupt feature may also be used to
generate up to 8 edge selectable external interrupts.
Figure 19 shows the Multi-Input Wake-up logic.
The Multi-Input Wake-up feature utilizes the L Port. The user
selects which particular L port bit (or combination of L Port
bits) will cause the device to exit the HALT or IDLE modes.
The selection is done through the register WKEN. The reg-
ister WKEN is an 8-bit read/write register, which contains a
control bit for every L port bit. Setting a particular WKEN bit
enables a Wake-up from the associated L port pin.
The user can select whether the trigger condition on the
selected L Port pin is going to be either a positive edge (low
to high transition) or a negative edge (high to low transition).
This selection is made via the register WKEDG, which is an
8-bit control register with a bit assigned to each L Port pin.
Setting the control bit will select the trigger condition to be a
negative edge on that particular L Port pin. Resetting the bit
selects the trigger condition to be a positive edge. Changing
an edge select entails several steps in order to avoid a
Wake-up condition as a result of the edge change. First, the
associated WKEN bit should be reset, followed by the edge
select change in WKEDG. Next, the associated WKPND bit
should be cleared, followed by the associated WKEN bit
being re-enabled.
An example may serve to clarify this procedure. Suppose we
wish to change the edge select from positive (low going high)
to negative (high going low) for L Port bit 5, where bit 5 has
previously been enabled for an input interrupt. The program
would be as follows:
FIGURE 18. Wake-up from IDLE
(Continued)
32
If the L port bits have been used as outputs and then
changed to inputs with Multi-Input Wake-up/Interrupt, a
safety procedure should also be followed to avoid wake-up
conditions. After the selected L port bits have been changed
from output to input but before the associated WKEN bits are
enabled, the associated edge select bits in WKEDG should
be set or reset for the desired edge selects, followed by the
associated WKPND bits being cleared.
This same procedure should be used following reset, since
the L port inputs are left floating as a result of reset.
The occurrence of the selected trigger condition for Multi-
Input Wake-up is latched into a pending register called WK-
PND. The respective bits of the WKPND register will be set
on the occurrence of the selected trigger edge on the corre-
sponding Port L pin. The user has the responsibility of clear-
ing these pending flags. Since WKPND is a pending register
for the occurrence of selected wake-up conditions, the de-
vice will not enter the HALT mode if any Wake-up bit is both
enabled and pending. Consequently, the user must clear the
pending flags before attempting to enter the HALT mode.
WKEN and WKEDG are all read/write registers, and are
cleared at reset. WKPND register contains random value
after reset.
RBIT
SBIT
RBIT
SBIT
5, WKEN
5, WKEDG
5, WKPND
5, WKEN
; Disable MIWU
; Change edge polarity
; Reset pending flag
; Enable MIWU
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