lan8720 Standard Microsystems Corp., lan8720 Datasheet - Page 49

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

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i
5.2.2
5.3
5.3.1
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
Note: The ENERGYON bit 17.1 is defaulted to a ‘1’ at the start of the signal acquisition process,
Alternate Interrupt System
The Alternative method is enabled by writing a ‘1’ to 17.6 (ALTINT).
To set an interrupt, set the corresponding bit of the in the Mask Register 30, (see
To Clear an interrupt, either clear the corresponding bit in the Mask Register (30), this will de-assert
the nINT output, or Clear the Interrupt Source, and write a ‘1’ to the corresponding Interrupt Source
Flag. Writing a ‘1’ to the Interrupt Source Flag will cause the state machine to check the Interrupt
Source to determine if the Interrupt Source Flag should clear or stay as a ‘1’. If the Condition to De-
Assert is true, then the Interrupt Source Flag is cleared, and the nINT is also de-asserted. If the
Condition to De-Assert is false, then the Interrupt Source Flag remains set, and the nINT remains
asserted.
For example 30.7 is set to ‘1’ to enable the ENERGYON interrupt. After a cable is plugged in,
ENERGYON (17.1) goes active and nINT will be asserted low.
To de-assert the nINT interrupt output, either.
Note: The ENERGYON bit 17.1 is defaulted to a ‘1’ at the start of the signal acquisition process,
Carrier Sense
The carrier sense is output on CRS. CRS is a signal defined by the MII specification in the IEEE 802.3u
standard. The LAN8720 asserts CRS based only on receive activity whenever the transceiver is either
Miscellaneous Functions
ENERGYON
Auto-Negotiation
complete
Remote Fault
Detected
Link Down
Auto-Negotiation
LP Acknowledge
Parallel
Detection Fault
Auto-Negotiation
Page Received
FLAG
therefore the Interrupt source flag 29.7 will also read as a ‘1’ at power-up. If no signal is
present, then both 17.1 and 29.7 will clear within a few milliseconds.
therefore the Interrupt source flag 29.7 will also read as a ‘1’ at power-up. If no signal is
present, then both 17.1 and 29.7 will clear within a few milliseconds.
1. Clear the ENERGYON bit (17.1), by removing the cable, then writing a ‘1’ to register 29.7.
Or
2. Clear the Mask bit 30.1 by writing a ‘0’ to 30.1.
Table 5.38 Alternative Interrupt System Management Table
17.1
1.5
1.4
1.2
5.14
6.4
6.1
INTERRUPT SOURCE
Link Status
ENERGYON
Auto-Negotiate
Complete
Remote Fault
Acknowledge
Parallel Detection
Fault
Page Received
DATASHEET
49
Rising 17.1
Rising 1.5
Rising 1.4
Falling 1.2
Rising 5.14
Rising 6.4
Rising 6.1
ASSERT nINT
EVENT TO
17.1 low
1.5 low
1.4 low
1.2 high
5.14 low
6.4 low
6.1 low
DE-ASSERT
CONDITION
TO
Revision 1.0 (04-15-09)
Table
5.38).
29.7
29.6
29.5
29.4
29.3
29.2
29.1
CLEAR
BIT TO
nINT