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551 73M291 0/291 OAMicrocontrollerREGISTER DESCRIPTION (continued)BIT 4 USR50 PolarityBIT 4 determines which edge or level is used in the wakeup detection circuit. A low level selects a rising transitionand the true pin value of USR50tothe wakeup combinatorial circuit. When this bit is set to a 1, a falling transitionand complemented USR50 value is presented to the wakeup combinatorial circuit.BIT 3 USR51 PolarityBIT 3 determines which edge or level is used in the wakeup detection circuit. A low level selects a rising transitionand the true pin value of USR51 to the wakeup combinatorial circuit. When this bit is set to a 1 , a falling transitionand complemented USR51 value is presented to the wakeup combinatorial circuit.BIT 2 USR50 Edge Activity EnabledWhen BIT 2 is set to a 1, a transition of USR50 of the appropriate level as dictated by BIT 4, will wake up theprocessor. If this bit is reset to a 0, edge activity on this pin is ignored.BIT 1 USR51 Edge Activity EnabledWhen BIT 1 is set to a 1, a transition of USR50 of the appropriate level as dictated by BIT 3, will wake up theprocessor. If this bit is reset to a 0, edge activity on this pin is ignored. .BIT 0 Combinatorial and of USR50 and USR51 Level EnabledWhen BIT 0 is set to a 1, the value USR50 or its complimented value as dictated by BIT3, ANDed with the valueUSR51 or its complimented value as dictated by BIT 2, will wake up the processor. If this bit is reset to a 0, thelevels of USR50 and USR5i are ignored.USR50 USR51 BIT4 BIT3 BIT2 BIT 1 BITO WAKEUP* * * * 0 0 0 NO0-1 * 0 * 1 * * YES1-0 * 1 * 1 * * YES* 0-1 * 0 * 1 * YES* 1-0 * 1 * 1 * YES0 0 1 1 * * 1 YES1 0 0 1 * * 1 YES0 1 1 0 * * 1 YES1 1 0 0 * * 1 YES* = Don't care.4-22