Si3453
Rev. 1.3 17
5. Register Interface
The registers types are described in the following sections.
5.1. Interrupt (Registers 0x00–0x01)
An interrupt (INT pin low) is generated if any bit of the Interrupt register (register 0x00) is true. The Interrupt register
contains the information about which port is generating the interrupt or if the interrupt is due to a global event.
The port interrupt is generated by the port event register masked by the interrupt mask register.
Port event = (t
START
Event AND t
START
mask) OR (tI
CUT
Event AND tI
CUT
mask) OR (Rgood_CLS_event AND
Rgood_CLS_mask) OR (DET_COMPL_EVENT AND DET_COMPL_MASK) OR (PwrGood_change AND
Pwrgood_change_MASK) OR (Penable_event AND Penable_mask)
The device event bit of the interrupt register is set if there is a change in the V
EE
or temperature status in register
0x1D. Reading 0x1D clears the event.
5.2. Port Event (Registers 0x02–0x05)
This register contains bits that become true if the event has occurred. The registers are Clear On Read (COR) so
that reading these registers will clear the INT
pin if the INT pin is being held low due to a port event.
t
START
is an event bit indicating an overload occurred for all but 5 ms of the initial 60 ms start up time.
tI
CUT
is an event bit indicating that an overload condition has existed for greater than 60 ms after the first 60 ms.
tI
CUT
has a 16:1 up/down counter so that, if the overload is present at less than a 6.66% cycle, the port will not
shut down. Overload is defined as I>I
CUT
or port voltage not within 2 V of V
EE
. The port is turned off on this
event. A tI
CUT
event is also generated if the port is shutdown due to an overload or due to the protection clamp
turning on. If the port is set to auto mode, it will attempt to re-power after >750 ms if there is a good detection
signature.
Rgood CLS indicates classification has been completed. Classification is only attempted after an Rgood; so, if
this bit is set, it indicates that detection gave an Rgood and classification is complete.
DET compl indicates the completion of a detection cycle. Normally, this bit will be masked. The DET complete
bit is used for legacy detection via modified link pulses. If the link pulse is returned indicating a PD is present,
then, normally, a detection is done, and the port is powered only if the result is not a short. In some cases, it
may be desirable to deny power to a port where an overload has been detected until the port is unplugged. In
this case, the Ropen result will be used to indicate the port has been unplugged and detection and classification
can resume.
Disconnect event indicates a disconnect has occurred. DC power was removed due to the dc disconnect.
Overload conditions or loss of V
EE
turns off ports but does not generate a disconnect event.
Pgood indicates the port has been turned on and did not shut down during the Tstart time.
Penable indicates a port has been turned on.
5.3. Port Status (Registers 0x06–0x09)
These registers specify the port status. They are read-only registers.
Pwr good indicates that the port has been turned on and the port voltage is within 2 V of V
EE
.
Pwr Enable indicates the port has been turned on.
The three class status bits indicate the last classification result for that port. If a classification has not been done or
if the port is shut down with no new classification result, the class status is reported as unknown.
The three detect status bits indicate the last detection result for that port. If a detection has not been done or if the
port is shut down with no new detection result, the detection status is reported as unknown.
