80221 datasheet(26/91 Pages) LSI

26 / 91 page

80220/80221

MD400159/E

3.18.2 Diagnostic Loopback

A diagnostic loopback mode can also be selected by

setting the loopback bit in the MI serial port Control

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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