
Block Diagram
Interval Timers
The PBC has three
❏Counter 0 is associated with IRQ0 and can be used for system timing functions, such as timer interrupt for a
❏Counter 1 is used to generate a refresh request signal for ISA memory. This timer is not used.
❏Counter 2 provides the tone for the Speaker output function. This timer is not used.
These counters are driven with a 14.31818 MHz clock source.
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Real-Time Clock/NVRAM/Watchdog Timer Function
The MCPN750A employs an
❏A
❏A SNAPHAT battery housing a crystal along with the battery.
The SNAPHAT battery package is socket mounted on top of the M48T559 device. The battery housing is keyed to prevent reverse insertion. Since this is a lithium battery, be sure and observe the warnings and steps in the section titled Replacing Lithium Batteries in this chapter when replacing this battery.
The output of the watchdog timer is logically ORed onboard to provide a hard reset. The interrupt output generates an ISA interrupt.
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