2.5.3 Power State D2

Power state D2 is a lower power state than D1. In this state the

LSI53C875A core is placed in the coma mode. The following PCI

Configuration Space command register enable bits are suppressed:

I/O Space Enable

Memory Space Enable

Bus Mastering Enable

SERR/Enable

Enable Parity Error Response

Thus, the memory and I/O spaces cannot be accessed, and the LSI53C875A cannot be a PCI bus master. Furthermore, all interrupts are disabled when in power state D2. If changed from power state D2 to power state D0, the previous values of the PCI command register are restored. Also, any pending interrupts before the function entered power state D2 are asserted.

2.5.4 Power State D3

Power state D3 is the minimum power state, which includes settings called D3hot and D3cold. D3hot allows the device to transition to D0 using software. The LSI53C875A is considered to be in power state D3cold when power is removed from the device. D3cold can transition to D0 by applying VCC and resetting the device. Furthermore, the device's soft reset is continually asserted while in power state D3, which clears all pending interrupts and 3-states the SCSI bus. In addition, the device's PCI command register is cleared and the Clock Quadrupler is disabled, which results in additional power savings.

Power Management

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LSI 53C875A technical manual Power State D2, Power State D3