Mpc8540 Real-Time Clock Input; Mpc8540 Lbc Clock Divisor - Motorola MVME3100 Programmer's Manual

Chapter 2 Programming Details

MPC8540 Real-Time Clock Input

The MPC8540 real-time clock (RTC) input is driven by a 1 MHz clock generated by the control and
timers PLD. This provides a fixed clock reference for the RTC that software can use as a known timing
reference. To select this 1 MHz clock as the RTC timer reference, software must set the SEL_TBCLK
bit in the MPC8540 HID0 register.

MPC8540 LBC Clock Divisor

The MPC8540 LBC clock output is used by the control and timers PLD. The LBC clock is derived from
a divide by 2, 4 or 8 ratio of the internal CCB (core complex bus) clock as determined by the clock ratio
register (LCRR[CLKDIV]). For proper operation of the local bus, CLKDIV must be set for divide by 8,
which is the default value. The software must leave this register configured for divide by 8 during
initialization.
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MVME3100 Programmer's Guide (V3100A/PG1)