SMSC LAN8720i User Manual
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Revision 1.0 (05-28-09)
48
SMSC LAN8720/LAN8720i
DATASHEET
5.2
Interrupt Management
The Management interface supports an interrupt capability that is not a part of the IEEE 802.3
specification. It generates an active low asynchronous interrupt signal on the nINT output whenever
certain events are detected as setup by the Interrupt Mask Register 30.
specification. It generates an active low asynchronous interrupt signal on the nINT output whenever
certain events are detected as setup by the Interrupt Mask Register 30.
The Interrupt system on the SMSC The LAN8720 has two modes, a Primary Interrupt mode and an
Alternative Interrupt mode. Both systems will assert the nINT pin low when the corresponding mask
bit is set, the difference is how they de-assert the output interrupt signal nINT.
Alternative Interrupt mode. Both systems will assert the nINT pin low when the corresponding mask
bit is set, the difference is how they de-assert the output interrupt signal nINT.
The Primary interrupt mode is the default interrupt mode after a power-up or hard reset, the Alternative
interrupt mode would need to be setup again after a power-up or hard reset.
interrupt mode would need to be setup again after a power-up or hard reset.
5.2.1
Primary Interrupt System
The Primary Interrupt system is the default interrupt mode, (Bit 17.6 = ‘0’). The Primary Interrupt
System is always selected after power-up or hard reset.
System is always selected after power-up or hard reset.
To set an interrupt, set the corresponding mask bit in the interrupt Mask register 30 (see
).
Then when the event to assert nINT is true, the nINT output will be asserted.
When the corresponding Event to De-Assert nINT is true, then the nINT will be de-asserted.
Note 5.1
If the mask bit is enabled and nINT has been de-asserted while ENERGYON is still high,
nINT will assert for 256 ms, approximately one second after ENERGYON goes low when
the Cable is unplugged. To prevent an unexpected assertion of nINT, the ENERGYON
interrupt mask should always be cleared as part of the ENERGYON interrupt service
routine.
nINT will assert for 256 ms, approximately one second after ENERGYON goes low when
the Cable is unplugged. To prevent an unexpected assertion of nINT, the ENERGYON
interrupt mask should always be cleared as part of the ENERGYON interrupt service
routine.
Table 5.37 Interrupt Management Table
MASK
INTERRUPT SOURCE
FLAG
INTERRUPT SOURCE
EVENT TO
ASSERT nINT
EVENT TO
DE-ASSERT nINT
30.7
29.7
ENERGYON
17.1
ENERGYON
Rising 17.1
(
(
Falling 17.1 or
Reading register 29
Reading register 29
30.6
29.6
Auto-Negotiation
complete
complete
1.5
Auto-Negotiate
Complete
Complete
Rising 1.5
Falling 1.5 or
Reading register 29
Reading register 29
30.5
29.5
Remote Fault
Detected
Detected
1.4
Remote Fault
Rising 1.4
Falling 1.4, or
Reading register 1 or
Reading register 29
Reading register 1 or
Reading register 29
30.4
29.4
Link Down
1.2
Link Status
Falling 1.2
Reading register 1 or
Reading register 29
Reading register 29
30.3
29.3
Auto-Negotiation
LP Acknowledge
LP Acknowledge
5.14
Acknowledge
Rising 5.14
Falling 5.14 or
Read register 29
Read register 29
30.2
29.2
Parallel Detection
Fault
Fault
6.4
Parallel
Detection Fault
Detection Fault
Rising 6.4
Falling 6.4 or
Reading register 6, or
Reading register 29
or
Re-Auto Negotiate or
Link down
Reading register 6, or
Reading register 29
or
Re-Auto Negotiate or
Link down
30.1
29.1
Auto-Negotiation
Page Received
Page Received
6.1
Page Received
Rising 6.1
Falling of 6.1 or
Reading register 6, or
Reading register 29
Re-Auto Negotiate, or
Link Down.
Reading register 6, or
Reading register 29
Re-Auto Negotiate, or
Link Down.