EVB8720 SMSC, EVB8720 Datasheet - Page 6

• Manufacturer Part Number: EVB8720
• Description: Ethernet Modules & Development Tools LAN8720 Design BRD
• Manufacturer: SMSC

Specifications of EVB8720

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Revision 1.1 (05-24-10)
2.2.3
50MHz
Clock
MAC
MAC
On-Board 50MHz Oscillator
Clocking and nINT/REFCLKO Pin Configuration (nINTSEL)
The nINT and REFCLKO functions share a common LAN8720A pin. This pin can operate in two
functional modes: nINT (Interrupt) Mode and REFCLKO Mode. The nINTSEL configuration strap is
used to select one of these two modes.
Additionally, the EVB8720 allows clock source selection in each mode, resulting in the four modes of
operation detailed in
via the on-board 50MHz oscillator. In REFCLKO mode, the clock can be sourced from one of the on-
board clock sources (25MHz crystal or 50MHz oscillator). The EVB8720 must be properly configured
for each mode as detailed in
Note: The nINTSEL configuration strap shares functionality with LED2. Therefore, LED2 may function
Off-Board 50MHz Clock
TXCLK
RXCLK
RXCLK
nINT Modes
nINT
nINT
or
active-high or active-low depending on the nINTSEL configuration. For additional information
on the functionality of the nINT/REFCLKO and LED2/nINTSEL pins, refer to the LAN8720A
Datasheet and LAN8720A schematics.
CLKIN
Figure 2.2 EVB8720 nINT & REFCLKO Modes of Operation
nINT
nINT
25MHz
25MHz
Crystal
Crystal
(OFF)
(OFF)
LAN8720A
LAN8720A
EVB8720
EVB8720
Figure
Oscillator
Oscillator
50MHz
50MHz
(OFF)
(ON)
2.2. In nINT mode, the clock can be sourced from the partner device or
Ethernet
Ethernet
Table
USER MANUAL
2.3.
6
On-Board 25MHz Crystal (Default Mode)
MAC
MAC
On-Board 50MHz Oscillator
REFCLKO Modes
RXCLK
RXCLK
EVB8720 Evaluation Board User Manual
REFCLKO
REFCLKO
25MHz
Crystal
25MHz
Crystal
(OFF)
(ON)
LAN8720A
LAN8720A
EVB8720
EVB8720
Oscillator
Oscillator
50MHz
50MHz
(OFF)
(ON)
SMSC EVB8720
Ethernet
Ethernet