MIC2358 Datasheet, PDF (27/29 Pages) Micrel Semiconductor – IEEE 802.3af Octal Power Sourcing Equipment Controller

Micrel, Inc.
Programming Guide
There are several ways of turning on a port in a
system where the host manages the power budget.
The following example outlines one such method.
The ENABLE_L pin is high, so that the host can gain
control of the MIC2358YLQ before any attempt is
made to power ports. The host sets the classifies and
deny and event_hold bits in every port OPTION
register, and sets the classify bit in every port
CONTROL register. The host then unmasks the
valid_signature event in the global EVENT_MASK
register. The host then clears all the disable bits in
the port CONTROL registers, allowing the ports to
begin operation. The host then waits for an event,
either by monitoring the global SRQ register, or by
waiting for the /SMBINT to be asserted. Once an
event occurs, the host can read the global SRQ
register to figure out which port the event occurred on,
MIC2358YLQ
then read that port's EVENT register to make sure it
was a valid_signature event that occurred on that port
(the host may have chosen to unmask other events
besides valid_signature). The host then reads the
port's STATUS register to find out what level of
classification the PD presented to the PSE. The host
can then decide if it has enough power available to
power up this port at that classification level. If the
host decides to not to power up the port, then nothing
further needs to be done.
If the host does decide to power the port, then it must
clear the classify_and_deny bit in the port's OPTION
register. The next time this port is serviced, it will
repeat detection and classification, and power up the
port. The host can monitor the port's STATUS register
to see that the port gets powered up, then set the
classify_and_deny bit in the port's OPTION register so
that everything is ready to go for the next time a PD is
plugged into this port.
July 2010
27
M9999-070810