LAN9353 Datasheet, PDF (118/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
9.2.16.2 Connector Loopback
The device maintains reliable transmission over very short cables and can be tested in a connector loopback as shown
in Figure 9-7. An RJ45 loopback cable can be used to route the transmit signals from the output of the transformer back
to the receiver inputs. The loopback works at both 10 and 100 Mbps.
FIGURE 9-7:
CONNECTION LOOPBACK BLOCK DIAGRAM
10/100
Ethernet
MAC
TXD
RXD
Digital
Analog
TX
1
2
3
RX
XFMR
4
5
6
7
8
RJ45 Loopback Cable.
Created by connecting pin 1 to pin 3
and connecting pin 2 to pin 6.
9.2.17 100BASE-FX OPERATION
When set for 100BASE-FX operation, the scrambler and MTL-3 blocks are disable and the analog RX and TX pins are
changed to differential LVPECL pins and connect through external terminations to the external Fiber transceiver. The
differential LVPECL pins support a signal voltage range compatible with SFF (LVPECL) and SFP (reduced LVPECL)
type transceivers.
While in 100BASE-FX operation, the quality of the receive signal is provided by the external transceiver as either an
open-drain, CMOS level, Loss of Signal (SFP) or a LVPECL Signal Detect (SFF).
9.2.17.1 100BASE-FX Far End Fault Indication
Since Auto-Negotiation is not specified for 100BASE-FX, its Remote Fault capability is unavailable. Instead, 100BASE-
FX provides an optional Far-End Fault function.
When no signal is being received, the Far-End Fault feature transmits a special Far-End Fault Indication to its far-end
peer. The Far-End Fault Indication is sent only when a physical error condition is sensed on the receive channel.
The Far-End Fault Indication is comprised of three or more repeating cycles, each of 84 ONEs followed by a single
ZERO. This signal is sent in-band and is readily detectable but is constructed so as to not satisfy the 100BASE-X carrier
sense criterion.
Far-End Fault is implemented through the Far-End Fault Generate, Far-End Fault Detect, and the Link Monitor pro-
cesses. The Far-End Fault Generate process is responsible for sensing a receive channel failure (signal_status=OFF)
and transmitting the Far-End Fault Indication in response. The transmission of the Far-End Fault Indication may start or
stop at any time depending only on signal_status. The Far-End Fault Detect process continuously monitors the RX pro-
cess for the Far-End Fault Indication. Detection of the Far-End Fault Indication disables the station by causing the Link
Monitor process to de-assert link_status, which in turn causes the station to source IDLEs.
Far-End Fault is enabled by default while in 100BASE-FX mode via the Far End Fault Indication Enable (FEFI_EN) of
the PHY x Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x).
9.2.17.2 100BASE-FX Enable and LOS/SD Selection
100BASE-FX operation is enabled by the use of the FX mode straps (fx_mode_strap_1 and fx_mode_strap_2) and is
reflected in the 100BASE-FX Mode (FX_MODE) bit in the PHY x Special Modes Register (PHY_SPECIAL_MODES_x).
Loss of Signal mode is selected for both PHYs by the three level FXLOSEN strap input pin. The three levels correspond
to Loss of Signal mode for a) neither PHY (less than 1 V (typ.)), b) PHY A (greater than 1 V (typ.) but less than 2 V (typ.))
or c) both PHYs (greater than 2 V (typ.)). It is not possible to select Loss of Signal mode for only PHY B.
DS00001925A-page 118
 2015 Microchip Technology Inc.