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CDP1020 Datasheet PDF : 23 Pages
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CDP1020
REMREQ_EN bit is set. This event will transition the bay into
the Removal Requested state, flash the bay status LED
amber, and assert the ALRT pin to notify the OS.
The Device Removal Requested state is also entered when
the OS writes a %011 to the BAY_STREQ field in the BCERx.
In either case, the CDP1020 will enter the Device Removal
Requested state only if a device is inserted into the bay
(1394PRx & USBPRx = 0).
While in this state the bay status LED will flash amber at 1Hz.
Device Removal Allowed
The Device Removal Allowed state is the last of the five bay
states. This state can only be entered through an OS write to
the BCERx register. The CDP1020 hardware cannot
transition the bay state into Device Removal Allowed.
The CDP1020 will transition the bay state controller to the
Device Removal Allowed state when the OS writes a %100
to the BAY_STREQ field of the BCERx register. The
CDP1020 will enter this state if and only if there is a device
detected in the bay (1394PRx & USBPRx = 0).
The Device Removal Allowed state is defined as the last state
that a device is in before being removed by a user. All bay
controls, including PWREN outputs and solenoid control
through the LOCK_CTL bit, are available in this state. Typically,
though, a device in the Removal Allowed state will be disabled
with its VID supply off. From this state the OS may transition the
CDP1020 state controller into any other state (except for Bay
Empty, of course) by simply writing to the BAY_STREQ bits in
the BCER. Also, removal request events will be generated if the
REMREQ_EN bit is set and a user asserts the REMREQ input.
Finally, when in the Removal Allowed state, the CDP1020
will NOT generate a removal event if the device is removed
from the bay and the REMEVTWAK bit is clear. This allows
the OS to not be disturbed by the removal of a device that
has already been powered down. If the REMEVTWAK flag is
set, the CDP1020 will generate a removal event when a
device is removed (assuming the DEVSTSCHG_EN bit is
set). In any case, the CDP1020 will always transition the bay
state to Bay Empty upon the removal of a device, regardless
of the state of any of the control or status bits.
In the Device Removal Allowed state, the bay status LED
(LEDGx and LEDAx) outputs will be off.
State Transitions
The following tables illustrate the hardware (CDP1020
controlled) and software (OS controlled) state transitions for
the CDP1020 bay state controllers.
CURRENT
STATE
----
----
Device
Inserted
Device
Enabled
Removal
Requested
Device
Removal
Allowed
TABLE 2. HARDWARE EVENT BAY STATE TRANSITION TABLE
NEXT STATE HARDWARE EVENT
CONDITIONS
NOTES
Bay Empty
Power-On Reset
(no device present)
Establish initial state.
Bay Empty
(device present)
Power-On Reset
A device occupying a bay at power-on time will not
necessarily cause DEVSTSCHG to be set.
Furthermore, since DEVSTSCHG_EN defaults to ‘0’
no bay state transition will result. Either the system
BIOS or the OS, upon loading, will automatically
enumerate all occupied bays and MUST clear
DEVSTSCHG if it was set.
Bay Empty
Device removed from
the bay.
Present bit(s) has
transitioned from 1 to 0
independent of the state
of DEVSTSCHG_EN.
Unexpected user behavior. The device was removed
prior to being properly enabled by the OS. In this case
the software controlled interlock mechanism may have
been overridden.
Removal
Requested
User pressed the
hardware removal
request button, if
present
REMREQ_STS and
User requested device removal through the hardware
REMREQ_EN are both removal request button.
set.
Bay Empty
Device removed from
the bay.
Present bit(s) has
transitioned from 1 to 0
independent of the state
of DEVSTSCHG_EN.
Unexpected user behavior. The device was removed
prior to completion of the proper removal request
sequence. In this case the software controlled interlock
mechanism may have been overridden.
Bay Empty
Device was removed
from the bay
Present bit(s) has
transitioned from 1 to 0
independent of the state
of DEVSTSCHG_EN.
Completion of normal device removal sequence.
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