COP8SA-DM National Semiconductor, COP8SA-DM Datasheet - Page 212

• Manufacturer Part Number: COP8SA-DM
• Description: MODULE DEBUGGING FOR COP8SA
• Manufacturer: National Semiconductor

Specifications of COP8SA-DM

• Module/board Type: Debugger Module
• For Use With/related Products: Cop 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *COP8SA-DM

Power-on wakeup is a technique used in battery powered applications such as electronic
keys or digital scales to save battery power. Instead of using the HALT mode when the
application is not in use, the microcontroller device is powered off. If there is only one
input switch in the application, the implementation is simple. This switch is put in series
with the battery, providing power to the circuit when the switch is closed.
If there is more than one switch, power-on wakeup can be achieved by using an NPN
transistor and one resistor per switch as shown in Figure 4-8. Here, the circuit ground is
connected to the battery negative terminal via the NPN transistor. If the base is floating,
it will not conduct. If the base is pulled to V
conduct, powering up the circuit.
An alternative technique is shown in Figure 4-9. Here the positive terminal of the
battery is connected to the V
switch is pressed, power is applied to the V
connected to open switches to ground. If the switch is closed, the voltage on the switch
will be V
L pin, the COP device would be driven outside the operating specification. Therefore,
series protection resistors are used on all Port L pins connected to the switches.
4-20
COP8SAx7 APPLICATION IDEAS
CC
plus the diode voltage drop. If this potential were directly applied to the Port
Figure 4-8 Power Wakeup Using An NPN Transistor
CC
Vcc
line via a switch, a diode and two resistors per line. If a
L0
L1
L2
L3
COP8SAx7
CC
GND
Vcc
line. The pull-down resistors pull any ports
CC
via a current-limiting resistor, it will
+
+
Vcc