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This Technote
describes the relationship between the Power Manager on
PowerBook computers and the PC Card Manager 3.0.
Updated: [Feb 9 1998]
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PowerBook Power Management
(Sleep/Wake) and PC Card Manager 3.0
PowerBooks support a Sleep state in order to extend
battery life. Since PC Cards can consume a lot of power
(relatively speaking), PC Card Manager 3.0 works along with
the Mac OS to turn off power when the computer goes to
sleep. This provides some opportunities and responsibilities
for the developers of PC Card drivers and card enablers.
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What PC Card Manager 3.0 Does...
When your PowerBook goes to sleep
- PC Card Manager 3.0 will notify clients (with a
kPCCardPMSuspendMessage)
- PC Card Manager 3.0 saves the generic state of the
card (configuration registers, window mappings etc.)
- PC Card Manager 3.0 turns off power to the socket
When your PowerBook wakes up
- PC Card Manager 3.0 turns on power to the socket
- PC Card Manager 3.0 restores the generic state of the
card
- PC Card Manager 3.0 sends
kPCCardPMResumeMessage
notification to clients
When your PowerBook is idle
- depending on the settings of your PowerBook control
panel, after some period of time, the Mac OS will issue a
sleep request in order to determine if it is safe to put
the machine to sleep
- PC Card Manager 3.0 will get this request and send a
kPCCardPMSuspendRequest notification to all clients
- if any client objects to going to sleep (for example,
if it would disrupt a network connection), it should
return a value not equal to noErr from it's call back
function.
- if nobody vetoes this sleep request (PC CARD client
or non-client), the machine goes to sleep and PC CARD
clients will see a
kPCCardPMSuspendMessage
- when a sleep demand call is issued, PC Cards can
not reject the call; this is merely notification to your
card that the system is going to go to sleep, not a
request for sleep. See the
Power Manager chapter
ofInside Macintosh: Devices for more detail.
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What Card developers need to
do
Preserving Device Specific Dynamic Data
- if you are doing a driver for a PC CARD device that
has some data on a card that will go away if the power is
turned off, you are responsible for saving and restoring
it.
- you can save and restore this data in either the
device driver or a custom card enabler
- if you wish to save this data in a device driver:
- register the driver as a card services client
- when you get a
kPCCardPMSuspendMessage, save the
device specific data
- when you get a
kPCCardPMResumeMessage, restore the
device specific data
- if you wish to save this data in a custom card
enabler: (this might be the best choice for a
multi-function card)
- override
setPCCardPowerLevel
- save the device specific data on the card
- call
CEPowerManagement
- When waking up
- call
CEPowerManagement
- restore the device specific data on the card
Implementing a Low Power Mode
- We have defined three power states for PC Card
Manager 3.0 (
kPCCardPowerOn, kPCCardPowerOff and
kPCCardLowPower)
- PC Card Manager 3.0 only supports On and Off (Low is
considered to be On)
- If your card supports a Low power mode, you will need
a custom card enabler to support transitions to and from
this Low power mode - you will need to override
setPCCardPowerLevel to do so.
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Note:
in a future version of the PC Card Manager, we
intend to implement a function named PCCardSetPowerLevel
which could be called by a driver to turn power off
and/or low. This will make your driver very battery
friendly.
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References
PC Card 3.0 Manager SDK
Documentation
Inside Macintosh: Devices, chapter 6, the Power Manager
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Downloadables
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Acrobat version of this Note (48K)
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