Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
7.2.5.5Half Vs. Full-Duplex
Half-duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle network traffic and collisions. In this mode, the carrier sense signal, CRS, responds to both transmit and receive activity. If data is received while the PHY is transmitting, a collision results.
In full-duplex mode, the PHY is able to transmit and receive data simultaneously. In this mode, CRS responds only to receive activity. The CSMA/CD protocol does not apply and collision detection is disabled.
7.2.6HP Auto-MDIX
HP Auto-MDIX facilitates the use of CAT-3 (10 BASE-T) or CAT-5 (100 BASE-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 7.4 (See Note 7.1 on page 83), the PHY is capable of configuring the TXPx/TXNx and RXPx/RXNx twisted pair 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 through bit 15 (AMDIXCTRL) of the Port x PHY Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x). When AMDIXCTRL is cleared, Auto-MDIX can be selected via the auto_mdix_strap_x configuration strap. The MDIX can also be configured manually via the manual_mdix_strap_x if both the AMDIXCTRL bit and the auto_mdix_strap_x configuration strap are low. Refer to Section 3.2, "Pin Descriptions," on page 28 for more information on the configuration straps.
When bit 15 (AMDIXCTRL) of the Port x PHY Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x) is set to 1, the Auto-MDIX capability is determined by bits 13 and 14 of the Port x PHY Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x).
| RJ-45 8-pin straight-through | | | | RJ-45 8-pin cross-over for | |
| for 10BASE-T/100BASE-TX | | | | | 10BASE-T/100BASE-TX | |
| | | signaling | | | | | | signaling | |
TXPx | 1 | | | 1 | TXPx | | TXPx | 1 | | | 1 | TXPx |
| | |
TXNx | 2 | | | 2 | TXNx | | TXNx | 2 | | | 2 | TXNx |
| | |
RXPx | 3 | | | 3 | RXPx | | RXPx | 3 | | | 3 | RXPx |
| | |
Not Used | 4 | | | 4 | Not Used | | Not Used | 4 | | | 4 | Not Used |
Not Used | 5 | | | 5 | Not Used | | Not Used | 5 | | | 5 | Not Used |
RXNx | 6 | | | 6 | RXNx | | RXNx | 6 | | | 6 | RXNx |
| | |
Not Used | 7 | | | 7 | Not Used | | Not Used | 7 | | | 7 | Not Used |
Not Used | 8 | | | 8 | Not Used | | Not Used | 8 | | | 8 | Not Used |
| | | | | | | | | | | | |
| | Direct Connect Cable | | | | | | Cross-Over Cable | |
| | | | | | | | | | | | |
Figure 7.4 Direct Cable Connection vs. Cross-Over Cable Connection
7.2.7MII MAC Interface
The MII MAC Interface is responsible for the transmission and reception of the Ethernet data to and from the switch fabric MAC. The PHY is connected internally to the switch fabric MAC via standard MII signals per IEEE 802.3.
