Xerox 4540 Service Manual - Page 245
Power Reset and Initialization Sequences, E.1 Power-On Reset Sequence
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E A P P E N D I X Power Reset and Initialization Sequences This appendix describes the power-on and power-off reset sequences. ■ Section E.1, "Power-On Reset Sequence" on page E-1 ■ Section E.2, "Power-Off Sequence" on page E-4 E.1 Power-On Reset Sequence The power-on sequence is initiated as soon as power is applied or when the power button is pushed, depending on the BIOS settings. When the sequence is initiated, the main power supplies are enabled, then the hot-swap circuit for the main 12V rail is enabled. When 12V is up, the supplies are sequenced as follows: ■ 1.5V, 3.3V, and -12V ■ 1.8V, 2.5V, and 1.25V ■ Processor core voltage ■ 1.2V and 1.5V When all of the rails are within 5%, the voltage monitor chip waits for 210 mS then asserts ALL_POWERGOOD, which starts the boot sequence. The diagram in FIGURE E-1 shows the power-on sequence. TABLE E-1 defines the symbols used in the diagram and describes the power-on sequence timing parameters. E-1