Datasheet

LAN8710A/LAN8710AI
DS00002164B-page 24  2016 Microchip Technology Inc.
3.2.3 DISABLING AUTO-NEGOTIATION
Auto-negotiation can be disabled by setting the Auto-Negotiation Enable bit of the Basic Control Register to zero. The
device will then force its speed of operatio
n to reflect the information in the Basic Control Register (Speed Select bit and
Duplex Mode bit). These bits should be ignored when auto-negotiation is enabled.
3.2.4 HALF VS. FULL DUPLEX
Half duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle net-
work traffic and collisions. In this mode, the carrier sense signal
, CRS, responds to both transmit and receive activity. If
data is received while the transceiver is transmitting, a collision results.
In full duplex mode, the transceiver is able to transmit a
nd receive data simultaneously. In this mode, CRS responds
only to receive activity. The CSMA/CD protocol does not apply and collision detection is disabled.
3.3 HP Auto-MDIX Support
HP Auto-MDIX facilitates the use of CAT-3 (10BASE-T) or CAT-5 (100BASE-T) media UTP interconnect cable without
consideration of interface wiring scheme. If a user plugs in either a direct connect LAN cable, or a cross-over patch
cable, as shown in Figure 3-4, the device’s Auto-MDIX transceiver is capabl
e of configuring the TXP/TXN and RXP/RXN
pins for correct transceiver operation.
The internal logic of the device detects the TX and RX pins of
the connecting device. Since the RX and TX line pairs
are interchangeable, special PCB design considerations are needed to accommodate the symmetrical magnetics and
termination of an Auto-MDIX design.
The Auto-MDIX function can be disabled via the AMDIXCTRL bit in the Special Control/Status Indications Register.
FIGURE 3-4: DIRECT CABLE CONNECTION VS. CROSS-OVER CABLE CONNECTION
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
Direct Connect Cable
RJ-45 8-pin straight-through
for 10BASE-T/100BASE-TX
signaling
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
Cross-Over Cable
RJ-45 8-pin cross-over for
10BASE-T/100BASE-TX
signaling
3.4 MAC Interface
The MII/RMII block is responsible for communication with the MAC controller. Special sets of hand-shake signals are
used to indicate that valid received/transmitted data is present on the 4 bit receive/transmit bus.
The device must be configured in MII or RMII mod
e. This is done by specific pin strapping configurations. Refer to Sec-
tion 3.4.2.3, "MII vs. RMII Configuration," on page 26 for information on pin strapping and how the pins are mapped
differently.