Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Table 2.1 RMII Signals (continued)
BUFFER
TYPE
NUM PINS
NAME
SYMBOL
DESCRIPTION
Carrier Sense
/ Receive
Data Valid
CRS_DV
VO8
This signal is asserted to indicate the receive
medium is non-idle. When a 10BASE-T packet is
received, CRS_DV is asserted, but RXD[1:0] is
held low until the SFD byte (10101011) is
received.
Note:
Per the RMII standard, transmitted data
is not looped back onto the receive data
pins in 10BASE-T half-duplex mode.
1
PHY
Operating
Mode 2
Configuration
Strap
MODE2
VIS
(PU)
Combined with MODE0 and MODE1, this
configuration strap sets the default PHY mode.
See Note 2.1 for more information on
configuration straps.
Note:
Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 31 for
additional details.
Note 2.1 Configuration strap values are latched on power-on reset and system reset. Configuration
straps are identified by an underlined symbol name. Signals that function as configuration
straps must be augmented with an external resistor when connected to a load. Refer to
Section 3.7, "Configuration Straps," on page 31 for additional information.
Table 2.2 LED Pins
BUFFER
NUM PINS
NAME
SYMBOL
TYPE
DESCRIPTION
LED 1
LED1
O12
Link activity LED Indication. This pin is driven
active when a valid link is detected and blinks
when activity is detected.
Note:
Refer to Section 3.8.1, "LEDs," on
page 37 for additional LED information.
Regulator Off
Configuration
Strap
REGOFF
IS
(PD)
This configuration strap is used to disable the
internal 1.2V regulator. When the regulator is
disabled, external 1.2V must be supplied to
VDDCR.
When REGOFF is pulled high to VDD2A with
an external resistor, the internal regulator is
disabled.
1
When REGOFF is floating or pulled low, the
internal regulator is enabled (default).
See Note 2.2 for more information on
configuration straps.
Note:
Refer to Section 3.7.3, "REGOFF:
Internal +1.2V Regulator Configuration,"
on page 32 for additional details.
SMSC LAN8720A/LAN8720Ai
11
Revision 1.4 (08-23-12)
DATASHEET
SMSC [ SMSC CORPORATION ]
