Sun Microsystems 4000, 5000, 6000 manual Handling Boards and Assemblies Clock Board, Jtag

6

6.1 Handling Boards and Assemblies

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6.2 Clock Board

Caution – The chassis AC power cord must remain connected to ensure a proper ground.

Caution – The clock board and its modules have surface-mount components that can be broken by flexing the board.

To minimize the amount of board flexing, observe the following precautions:

•Hold the board only by the edges near the middle of the board, where the board stiffener is located. Do not hold the board only at the ends.

•When removing the board from an antistatic bag, keep the board vertical until you lay it on the Sun ESD mat.

•Do not place the board on a hard surface. Use a cushioned antistatic mat. The board connectors and components have very thin pins that bend easily.

•Do not use an oscilloscope probe on the components. The soldered pins are easily damaged or shorted by the probe point.

•Transport the board in an antistatic bag.

•Be careful not to drag boards across surfaces as board components are easily damaged.

There is one clock board to a system. The clock board provides:

•Programmable system and processor clock

•Serial, keyboard, and mouse ports for the console

•Centralized Time-of-day (TOD) chip that includes NVRAM

•Centralized reset logic

•Status and control of power supplies

The clock board consists of the following subsystems:

•Console Bus

•Clocks

•Reset logic

•JTAG

•Centerplane connector signals

6-2 Ultra Enterprise 6000/5000/4000 Systems Manual—November 1996