
DM9331
100 Mbps Twisted Pair/Fiber Ethernet Media Converter Chip
Preliminary 17
Version: DM9331-DS-P02
September 21, 2001
Power Reduced Mode
The Signal detect circuit is always turned on to monitor
whether there is any signal on the media. In case of cable
disconnection, DM9331 will automatically turn off the power
and enter the Power Reduced mode, regardless of its
operation mode being N-way auto-negotiation or forced
mode. While in the Power Reduced mode, the transmit
circuit will continue sending out fast link pules with minimum
power consumption. If a valid signal is detected from the
media, which might be N-way fast link pules, 10Base-T
normal link pules, or 100Base-TX MLT3 signals, the device
wakes up and resumes normal operation mode.
Automatic reduced power down mode can be disabled by
writing Zero to Reg.16.4.
Power Down Mode
Power Down mode is entered by setting Reg.0.11 to ONE or
pulling PWRDWN pin high, which disables all transmit,
receive functions and MCI interface functions except the
MDC/MDIO management interface.
Reduced Transmit Power Mode
Additional Transmit power reduction can be gained by
designing with 1.25:1 turns ration magnetics on its TX side
and using a 8.5K
Ω
resistor on BGRES and BGRESG pins,
and the TX+/TX- pull-high resistors being changed from 50
Ω
to 78
Ω
. This configuration could reduce about 20% of
transmit power.
Link Fault Propagation
The DM9331 will propagate link fault signals from
media to another DM9331. If link fault happens, the
DM9331 will send out fault signals to another DM9331.
In FX mode, their are two types of link failure, receive
link failure or remote fault (receive far end fault).In the
event of a fiber receive link failure, the DM9331 will
send out an FX fault signal. The DM9331 will send out
a far end fault signal to the fiber optic media, if the
DM9331 receive the fault signal from the other device.
In TP mode, In the event of a TP receive link failure,
the DM9331 will send out a TP fault signal. The
DM9331 will stop to transmit idle signal to the CAT5
media, if the DM9331 receive the fault signal from the
other device.