lan8720 Standard Microsystems Corp., lan8720 Datasheet - Page 48

• Manufacturer Part Number: lan8720
• Description: Small Footprint Rmii 10/100 Ethernet Transceiver With Hp Auto-mdix Support
• Manufacturer: Standard Microsystems Corp.

Revision 1.0 (04-15-09)
5.2
5.2.1
30.7
30.6
30.5
30.4
30.3
30.2
30.1
MASK
29.7
29.6
29.5
29.4
29.3
29.2
29.1
INTERRUPT SOURCE
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.
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.
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.
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.
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
Interrupt Management
Auto-Negotiation
Remote Fault
Link Down
Auto-Negotiation
Parallel Detection
Auto-Negotiation
ENERGYON
complete
Detected
LP Acknowledge
Fault
Page Received
FLAG
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.
Table 5.37 Interrupt Management Table
17.1
1.5
1.4
1.2
5.14
6.4
6.1
INTERRUPT SOURCE
DATASHEET
ENERGYON
Auto-Negotiate
Complete
Remote Fault
Link Status
Acknowledge
Parallel
Detection Fault
Page Received
48
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Rising 17.1
(Note
Rising 1.5
Rising 1.4
Falling 1.2
Rising 5.14
Rising 6.4
Rising 6.1
ASSERT nINT
EVENT TO
5.1)
SMSC LAN8720/LAN8720i
Falling 17.1 or
Reading register 29
Falling 1.5 or
Reading register 29
Falling 1.4, or
Reading register 1 or
Reading register 29
Reading register 1 or
Reading register 29
Falling 5.14 or
Read register 29
Falling 6.4 or
Reading register 6, or
Reading register 29
or
Re-Auto Negotiate or
Link down
Falling of 6.1 or
Reading register 6, or
Reading register 29
Re-Auto Negotiate, or
Link Down.
DE-ASSERT nINT
EVENT TO
Table
Datasheet
5.37).