LAN9353 Datasheet, PDF (117/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
TABLE 9-9:
12
13
14
15
MATCH CASE ESTIMATED CABLE LENGTH (CBLN) LOOKUP
91
102
113
123
Note: For a properly terminated cable (Match case), there is no reflected signal. In this case, the TDR Channel
Length field is invalid and should be ignored.
9.2.16 LOOPBACK OPERATION
The PHYs may be configured for near-end loopback and connector loopback. These loopback modes are detailed in
the following subsections.
9.2.16.1 Near-end Loopback
Near-end loopback mode sends the digital transmit data back out the receive data signals for testing purposes, as indi-
cated by the blue arrows in Figure 9-6. The near-end loopback mode is enabled by setting the Loopback (PHY_LOOP-
BACK) bit of the PHY x Basic Control Register (PHY_BASIC_CONTROL_x) to “1”. A large percentage of the digital
circuitry is operational in near-end loopback mode because data is routed through the PCS and PMA layers into the
PMD sublayer before it is looped back. The COL signal will be inactive in this mode, unless Collision Test Mode
(PHY_COL_TEST) is enabled in the PHY x Basic Control Register (PHY_BASIC_CONTROL_x). The transmitters are
powered down regardless of the state of the internal MII TXEN signal.
FIGURE 9-6:
NEAR-END LOOPBACK BLOCK DIAGRAM
10/100
Ethernet
MAC
TXD
RXD
Digital
X ^TX
X ^RX
Analog
XFMR
CAT-5
 2015 Microchip Technology Inc.
DS00001925A-page 117