LAN9353 Datasheet, PDF (114/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
9.2.15.1 Time Domain Reflectometry (TDR) Cable Diagnostics
The PHYs provide TDR cable diagnostics which enable the detection of open or shorted cabling on the TX or RX pair,
as well as cable length estimation to the open/short fault. To utilize the TDR cable diagnostics, Auto-MDIX and Auto
Negotiation must be disabled, and the PHY must be forced to 100 Mbps full-duplex mode. These actions must be per-
formed before setting the TDR Enable bit in the PHY x TDR Control/Status Register (PHY_TDR_CONTROL_STAT_x).
With Auto-MDIX disabled, the TDR will test the TX or RX pair selected by register bit 27.13 (Auto-MDIX State (AMDIX-
STATE)). Proper cable testing should include a test of each pair. TDR cable diagnostics is not appropriate for 100BASE-
FX mode. When TDR testing is complete, prior register settings may be restored. Figure 9-5 provides a flow diagram of
proper TDR usage.
FIGURE 9-5:
TDR USAGE FLOW DIAGRAM
Start
Disable ANEG and Force 100Mb Full-
Duplex
Write PHY Reg 0: 0x2100
Disable AMDIX and Force MDI (or MDIX)
Write PHY Reg 27: 0x8000 (MDI)
- OR -
Write PHY Reg 27: 0xA000 (MDIX)
Enable TDR
Write PHY Reg 25: 0x8000
Check TDR Control/Status Register
Read PHY Reg 25
TDR Channel Status Complete?
NO
Reg 25.8 == 0
YES
Reg 25.8 == 1
Save:
TDR Channel Type (Reg 25.10:9)
TDR Channel Length (Reg 25.7:0)
MDIX Case Tested?
Repeat Testing
in MDIX Mode
YES
Done
DS00001925A-page 114
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