80220 Datasheet, PDF (26/91 Pages) LSI Computer Systems – 100BASE-TX/10BASE-T Ethernet Media Interface Adapter

80220/80221
3.18.2 Diagnostic Loopback
A diagnostic loopback mode can also be selected by
setting the loopback bit in the MI serial port Control
register. When diagnostic loopback is enabled, TXD[3:0]
data is looped back onto RXD[3:0], TX_EN is looped back
onto CRS, RX_DV operates normally, the TP receive and
transmit paths are disabled, the transmit link pulses are
halted, and the Half/Full Duplex modes do not change.
Diagnostic loopback mode can not be enabled when the
FBI interface is selected.
3.19 AUTOMATIC JAM
3.19.1 100 Mbps
The 80220/80221 has an automatic JAM feature which will
cause the device to automatically transmit a JAM packet if
receive activity is detected. If automatic JAM is enabled,
then the following JAM packet will be transmitted on TPO±
when the JAM pin is asserted active low and receive
activity is detected on TP inputs (expressed in 5B code
words):
/J/K/5/5/5/5/5/5/5/5/5/5/5/5/5/D/H/H/H/H/H/H/H/H/T/R/
This automatic JAM feature is enabled when the RX_EN/
JAM pin is programmed to be a JAM input . RX_EN/JAM
can be configured to be a JAM input by appropriately
setting the R/J configuration bit in the MI serial port
Configuration 2 register.
3.19.2 10 Mbps
The JAM feature for 10 Mbps mode is identical to 100
Mbps mode except: (1) the JAM packet transmitted on
TPO± is composed of standard 62 bit preamble (alternat-
ing 1,0) followed by SFD (11) followed by 32 bits of
alternating 1,0 pattern.
3.20 RESET
The 80220/80221 is reset when either (1) VCC is applied
to the device, or (2) the reset bit is set in the MI serial port
Control register. When reset is initiated, an internal
power-on reset pulse is generated which resets all internal
circuits, forces the MI serial port bits to their default values,
and latches in new values for the MI address. After the
power-on reset pulse has finished, the reset bit in the MI
serial port Control register is cleared and the device is
ready for normal operation. The device is guaranteed to be
ready for normal operation 500 mS after the reset was
initiated.
3.21 POWERDOWN
The 80220/80221 can be powered down by setting the
powerdown bit in the MI serial port Control register. In
powerdown mode, the TP outputs are in high impedance
state, all functions are disabled except the MI serial port,
and the power consumption is reduced to a minimum. The
device is guaranteed to be ready for normal operation 500
mS after powerdown is deasserted.
3.22 OSCILLATOR
The 80220/80221 requires a 25 Mhz reference frequency
for internal signal generation. This 25 Mhz reference
frequency is generated by either connecting an external 25
MHz crystal between OSCIN and GND or by applying an
external 25Mhz clock to OSCIN.
3.23 LED DRIVERS
The PLED[5:2] outputs are open drain with a pullup resis-
tor and can drive LED's tied to VCC. The PLED[1:0]
outputs have both pullup and pulldown driver transistors
with a pullup resistor, so PLED[1:0] can drive LED's tied
to either VCC or GND.
The PLED[5:0] outputs can be programmed through the
MI serial port to do 4 different functions: (1) Normal
Function (2) On, (3) Off, and (4) Blink. PLED[5:0] can be
programmed with the LED output select bits and the LED
Normal Function select bits in the MI serial port Configura-
tion 2 register.
When PLED[5:0] are programmed for their Normal Func-
tions, these outputs indicate specific events. There are
four sets of specific events that these outputs can indicate,
and they are described in Tables 5 and 6. The selection of
which set of events that these outputs indicate is deter-
mined by appropriately setting the LED Normal Function
select bits in the MI serial port Configuration 2 register.
The default Normal Functions for PLED[5:0] are Transmit
Activity, Receive Activity, Link 100, Activity, Full Duplex,
and Link 10, respectively. PLED5 and PLED4 are only
available on the 64L 80221 version.
When PLED[3:0] is programmed to be On, the LED output
driver go low, thus turning on the LED under user control.
When PLED[3:0] is programmed to be Off, the LED output
driver will turn off, thus turning off the LED under user
control. When PLED[3:0] is programmed to Blink, the LED
output driver will continuously blink at a rate of 100 mS on,
100 mS off.
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MD400159/E