PC87591L datasheet(112/437 Pages) NSC

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Embedded Controller Modules (Continued)

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Pending Clear Register (WKPCL2)

Controls the clearing (0) of the pending bits associated with the WUI20 through WUI27 inputs. For a detailed description of

the register see, the above description of the WKPCL1 register.

Location: 00 FFCE16

Type: WO

Pending Clear Register (WKPCL3)

Controls the clearing (0) of the pending bits associated with the WUI30 through WUI37 inputs. For a detailed description of

the register, see the above description of the WKPCL1 register.

Location: 00 FFD216

Type: WO

Pending Clear Register (WKPCL4)

Controls the clearing (0) of the pending bits associated with the WUI40 through WUI47 inputs. For a detailed description of

the register, see the above description of the WKPCL1 register.

Location: 00 FFD616

Type: WO

4.4.4

Usage Hints

1. When changing an edge select, perform the following steps to avoid a spurious wake-up condition, which may occur as

a result of the edge change:

a. Clear the associated WKENxx bit.

b. Select the required the edge in the WKEDGx register.

c. Clear the associated WKPDxx bit.

d. Re-enable the associated WKENxx bit.

2. The correct use of the Multi-Input Wake-Up circuit, which avoids false triggering of a wake-up condition, requires the

following sequence of actions. Use the same procedure following a Reset since the wake-up inputs are left floating, pro-

ducing unknown data on the MIWU input signals.

a. If the input originates from an I/O port, write to the port alternate function and, if required, direction register to set the

pin to interrupt inputs.

b. Clear the WKENAx register or, if a WKOxx interrupt is used, disable the interrupt via the ICU.

c. Write the WKEDGx register to select the desired type of edge sensitivity for each of the pins used.

d. Clear the WKPNDx register to cancel any pending bits.

e. Either set the WKENxx bits associated with the pins to be used, thus enabling them for the wake-up/interrupt function,

or re-enable the interrupt via the ICU.

3. On Reset, the WKEDGx registers are configured to select positive edge sensitivity for all wake-up inputs. To change the

edge sensitivity of an input signal while preventing the false triggering of a wake-up/interrupt condition, use the following

procedure.

a. Clear the WKENxx bit associated with the WUIxx input to disable that input.

b. Write to the WKEDGx register to select the new type of edge sensitivity for the specific input.

c. Clear the WKPDxx bit associated with the WUIxx input.

d. Set the WKENxx bit associated with the WUIxx input to re-enable it.

PC87591L Datasheet(PDF) 112 Page - National Semiconductor (TI)

PC87591L Datasheet(HTML) 112 Page - National Semiconductor (TI)

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