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Clock Interface

Figure 2 below presents the clocking scheme used by the module.

Figure 2: Clocking Scheme

The following are some clocking strategies that can be utilized:

  1. C1 sources its clock from the oscillator by enabling jumper J8, while C [2,3 or 4] can buffer this signal (IO-9) to any connection on the NuBus, e.g. A30. A short circuit can then be created between this interconnection, i.e. A30 and A31 by installing a jumper wire.
  2. C [2,3 or 4] buffer A31 to IO-9 thereby clocking C1. In this scenario, jumper J8 is removed and an external clock is supplied to A31.
  3. Jumper J8's strategic location makes it possible to insert a wire within the jumper and plug the other end into NuBus A31. If this is done, a termination resistor (discussed ahead) may be required between A31 and GND located on the NUBus connector.
  4. Make C1 use a separate clock, while C [2,3, and 4] share their clock from A31.

Irrespective of the clocking strategy, it is always important to consider the effects of clock skew.