LAN8720AI datasheet(29/79 Pages) SMSC

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Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support

Datasheet

SMSC LAN8720A/LAN8720Ai

Revision 1.4 (08-23-12)

DATASHEET

3.6

Interrupt Management

The device management interface supports an interrupt capability that is not a part of the IEEE 802.3

specification. This interrupt capability generates an active low asynchronous interrupt signal on the

nINT output whenever certain events are detected as setup by the Interrupt Mask Register.

The device’s interrupt system provides 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.

These modes differ only in how they de-assert the nINT interrupt output. These modes are detailed in

the following subsections.

Note: The Primary interrupt mode is the default interrupt mode after a power-up or hard reset. The

Alternative interrupt mode requires setup after a power-up or hard reset.

3.6.1

Primary Interrupt System

The Primary interrupt system is the default interrupt mode (ALTINT bit of the Mode Control/Status

mode, to set an interrupt, set the corresponding mask bit in the Interrupt Mask Register (see Table 3.2).

Then when the event to assert nINT is true, the nINT output will be asserted. When the corresponding

event to deassert nINT is true, then the nINT will be de-asserted.

Note 3.1

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.

Table 3.2 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

(Note 3.1)

Falling 17.1 or

Reading register 29

30.6

29.6

Auto-Negotiation

complete

1.5

Auto-Negotiate

Complete

Rising 1.5

Falling 1.5 or

Reading register 29

30.5

29.5

Remote Fault

Detected

1.4

Remote Fault

Rising 1.4

Falling 1.4, or

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

30.3

29.3

Auto-Negotiation

LP Acknowledge

5.14

Acknowledge

Rising 5.14

Falling 5.14 or

Read register 29

30.2

29.2

Parallel Detection

Fault

6.4

Parallel

Detection Fault

Rising 6.4

Falling 6.4 or

Reading register 6, or

Reading register 29

Re-Auto Negotiate or

Link down

30.1

29.1

Auto-Negotiation

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.

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