MIC2358YLQ Datasheet, PDF (23/29 Pages) Micrel Semiconductor – IEEE 802.3af Octal Power Sourcing Equipment Controller

Micrel, Inc.
MIC2358YLQ
Global Power_Setup Register
SMBus Address: 0x41
Read and Write
Bit 7
Bit 6
Bit 5
max_class
Bit 4
Bit 3
Bit 2
minimum_priority_new_power
Bit 1
Bit 0
minimum_priority_maintain_power
Name
Default
Description
max_class
Class 0
(Note 1)
Specifies the maximum class that will be powered after detection of a new
powered device. Possible values are shown following the port STATUS register
description.
minimum_priority_new_power Low
(Note 2)
Sets the minimum priority level for a port to be powered following detection of a
powered device. A port with a lower priority will go to the POWER_DENIED
state. Possible values are shown following the port OPTION register
description.
minimum_priority_maintain_
power
Low
(Note 3)
Sets the minimum priority level for a port to remain powered. A port with a lower
priority will go to the POWER_DENIED state. Possible values are shown
following the port OPTION register description.
Notes:
1. The max_class is defined independently in both global POWER_SETUP and port OPTION registers. After a PD has been classified, the detected
class is compared to these two values. If the PD is requesting more power than either of the max_class fields, then that port will not be powered.
Upon power-up or, reset, global max_class and all port max_class default to Class 0.
Examples: The host sets global max_class to Class 2, and Port 5 max_class to Class 1. A PD is plugged into port 1 and classifies as Class 0.
This is more power than allowed by global max_class, so power will be denied to port 1. Another PD is plugged into port 2 and classifies as Class
2. This is equal to global max_class and less than port 2's max_class (which defaulted to Class 0), so port 2 is powered up. A Class 2 PD is
plugged into port 5. This is equal to global max_class, but greater than port 5's max_class, so power is denied. Then a Class 1 PD is plugged
into port 5. This is less than global max_class and equal to port 5's max_class, so the port is powered.
2. When a valid PD is detected on a port, that port's priority level is compared to the minimum_priority_new_power field in the global
POWER_SETUP register. If the port's priority is equal to or greater than the minimum_priority_new_power, then the port will be powered up.
Otherwise, the port will go to the POWER_DENIED state of the state diagram.
3. When the value of the minimum_priority_maintain_power field in the global POWER_SETUP register is changed, the MIC2358YLQ will check this
against the priority level of all ports that are currently powered. If a port's priority level is equal to or greater than the
minimum_priority_maintain_power, then that port will continue being powered up. If a port's priority level is less than the
minimum_priority_maintain_power, then power will be removed from that port and it will go to the POWER_DENIED state of the state diagram.
Global Event_Mask Register
SMBus Address: 0x42
Read and Write
Bit 7 Bit 6
Bit 5
Bit 4
–
power
valid_
invalid_
_denied signature signature
Bit 3
short_circuit
Bit 2
overload
Bit 1
dc_mps_
absebt
Bit 0
ac_mps_absent
Name
Default
Description
power_denied
1
Masks all ports from responding to a power denied event.
valid_signature
1
Masks all ports from responding to a valid signature event.
invalid_signature
1
Masks all ports from responding to an invalid signature event.
short_circuit
1
Masks all ports from responding to a short circuit event.
overload
1
Masks all ports from responding to an overload event.
dc_mps_absent
1
Masks all ports from responding to a DC MPS dropout event.
ac_mps_absent
1
Masks all ports from responding to an AC MPS dropout event.
Note:
1. This port is associated with every port EVENT register. If any port has an event occur that is not masked by the global EVENT_MASK register,
then the /SMBINT pin will be asserted.
July 2010
23
M9999-070810