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The 10Base-T1L standard allows connected devices in building and factory automation, monitoring stations, and sensing applications to reach new lengths through single-pair Ethernet. Designing a robust system to handle the challenges of communicating over 1,000 meters requires careful consideration of the capabilities of an Ethernet PHY and the specifications of the cable. The DP83TD510E Single-Pair Ethernet (SPE) PHY is a 10Base-T1L, IEEE 802.3cg compliant Ethernet transceiver. The DP83TD510E’s 1.0 Vpp and 2.4 Vpp operating modes offer design flexibility in maximizing cable reach for building, factory and process automation, including intrinsic safety applications. The following sections discuss each of these features or tools.
Cable length considerations:
Each section provides background into the functionality of the PHY and guidance on how to design for each mode of operation.
The 802.3cg standard requires 10Base-T1L PHYs to support auto-negotiation in low-speed-mode (LSM). In LSM, the PHY sends differential Manchester encoded (DME) pages at 625 Kb/s to advertise its capabilities to its link partner.
In normal operation, the DP83TD510E utilizes 3-level Pulse Amplitude Modulation (PAM3) signal transmitted over a single differential pair at 7.5MBd. The 10Base-T1L standard is unique in that it specifies that a PHY may support an increase transmit and receive capability, boosting the PAM3 amplitude from 1.0 Vpp to 2.4 Vpp. The greater transmit capability helps the PHY overcome attenuation over long cable lengths to extend the maximum reach of the PHY.
The DP83TD510E supports hardware and software configurations to advertise 1.0 Vpp or 2.4 Vpp and 1.0 Vpp capability during auto-negotiation. It also has the capability to adapt the transmit voltage to 2.4 Vpp or 1.0 Vpp as determined during auto-negotiation. DP83TD510E by default advertises 1.0 Vpp only. If both 1.0 Vpp and 2.4 Vpp are advertised and the Link Partner also supports 2.4 Vpp, the DP83TD510E will be configured to 2.4 Vpp. The DP83TD510E offers LED based indication to indicate PHY is operating in 2.4 Vpp or 1.0 Vpp operating mode.
This strap defines the voltage level requested by PHY during Auto Negotiation. It is reflected in register 0x020E[12]. While using Force mode for link-up, the strap controls the output voltage and reflects in register 0x18F6[12].
Pin Name | Strap Name | Pin # | Default | Setting | |
---|---|---|---|---|---|
LED_2 | Strap7 | 28 | 0 | 0 | 1.0 Vpp |
1 | 2.4 Vpp |
Bit | Field | Type | Reset | Description |
---|---|---|---|---|
12 | CFG_INCR_TX_LVL | R/W | 0x0 | 1 = Enable 2.4 Vpp operating mode |
0 = Enable 1.0 Vpp operating mode |
Ethernet PHYs operate as either host or client when a network link is established. The host device uses a local clock to set the transmitter timing over the Ethernet port. The client device relies on the recovered clock from its received signal to set its transmitter timing operation. The DP83TD510 will resolve the Host-Client relationship through auto-negotiation when enabled.
The Host-Client configuration, as well as output voltage mode, can be set manually if auto-negotiation is disabled. The maximum cable reach of the PHY may be extended by forcing both the Host-Client relationship and output voltage operating mode. Specific cable characteristics may limit the reach of 10BASE-T1L’s low-speed auto-negotiation protocol by attenuating or distorting the DME over the channel. For example, a cable with high insertion loss around 625 kHz distorts the auto-negotiation pulses and the link partner may fail to complete the auto-negotiation process by not interpreting the received signal properly. Forcing the PHY into the desired mode of operation bypasses auto-negotiation and allows extended cable reach. The following configurations are offered by the DP83TD510E to enable "Force Mode". Please note, while using force mode, auto-negotiation shall be prevented by disabling MR_AN_ENABLE on both the DUT and link partner. Please see Table 3-3. One of the PHYs (DUT or link partner) shall be configured for host and the other for client.