This section summarizes the modem power management requirements. See also the specific power management requirements for each bus defined in Part 3 of this guide.
35. Device complies with device class power management reference specification
Required
The Communications Device Class Power Management Reference Specification, Version 1.0 or higher, provides definitions of the OnNow device power states (D0–D3) for these devices, including modems. The specification also covers the device functionality expected in each power state and the possible wake-up event definitions for the class.
Power states D0 and D3 are required for modems on power-managed buses, including PCI, CardBus, and USB.
36. Device supports wake-up events
Required
For PC 98, a required modem feature is the ability to cause a wake-up event on an incoming ring as defined in Communications Device Class Power Management Reference Specification. Notice that this applies for modems on power-managed buses, including PCI, CardBus, and USB.
The D2 power state is defined specifically for this purpose in the power management reference specification. The ability for a modem to cause a wake-up event from the D3 power state might also be possible and is recommend to realize better system power savings. To comply with this requirement, a modem must be able to cause a wake-up event from either the D2 state, the D3 state, or both states.
Because caller-ID reporting would be missed by PCs while in a sleep state, the ability for a modem to retain and repeat the last caller-ID reporting on demand is strongly recommended. The mechanism for doing this is described in Communications Device Class Power Management Reference Specification and in the V.voice and TIA-695 voice modem specifications.