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Technical Supplement
9.6.6
Standard User Controls
9-22
The user-controls circuit is illustrated in Figure 9-24.
The standard user controls consist of two momentary push-button switches
(On/Off and battery-check). The Of/Off button is an elastomeric contact switch,
and the battery-check button is a mechanical momentary switch.
The CPU input lines BAT_BTN and GO_BTN are normally pulled to the high
state by R71 and R78. Whenever a button is pressed, the CPU input line is
pulled low through R74 and R80. The switch contacts are debounced with C64
and C66. L11, L12, C126, and C123 provide a current path for ESD protection.
In addition to being read by the CPU, the On/Off button also activates the power
supply via the power control circuit. Note that the On/Off button has circuitry
on both the main PCB as well as the auxiliary PCB.
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