AM79C874VC AMD (ADVANCED MICRO DEVICES), AM79C874VC Datasheet - Page 26

• Manufacturer Part Number: AM79C874VC
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of AM79C874VC

• Lead Free Status / RoHS Status: Not Compliant

loopback is used to check the device’s connection on
the media side and the operation of its internal adaptive
equalizer, phase-locked loop, and digital wave shape
synthesizer. During remote loopback, signal detect
(SD) output is forced to logic zero. Note that remote
loopback operates only in 100BASE-TX mode.
External loopback can be accomplished using an ex-
ternal loopback cable with TX± connected to RX±. Ex-
ternal loopback works for both 10 Mbps and 100 Mbps
after setting Register 0, bit 8 to force full duplex and bit
13 to set the speed.
Reset
The NetPHY-1LP device can be reset in the three fol-
lowing ways:
1. During initial power on (with internal power on reset
2. At hardware reset. A logic low signal of no less than
3. At software reset. Write a 1 to MII Register 0, bit 15.
LED Port Configuration
The NetPHY-1LP device has several pins that are used
for both device configuration and LED drivers. These
pins set the configuration of the device on the rising
edge of RST and thereafter indicate the state of the re-
spective port. See Table for standard LED selections
and Table 5 for advanced LED selections.
The polarity of the LED drivers (Active-LOW or Active-
HIGH) is set at the rising edge of RST. If the pin is LOW
at the rising edge of RST, it becomes an active-HIGH
26
circuit).
155 µs pulse width applied to the RST pin.
D A T A
Am79C874
10 Mbps
100 Mbps
Link
Duplex
Tx Activity
Rx Activity
driver. If it is HIGH at the rising edge of RST, it becomes
an active-LOW driver.
Proper configuration requires pull-up or pull-down re-
sistors. As shown in the Pin Description sections, each
of the LED/Configuration pins has internal pull-up re-
sistors. If the pin’s LED functionality is not used, the pin
may still need to be terminated via an external pull-
down resistor according to the desired configuration.
The resistor value is not critical and can be in the range
of 1 kΩ to 10 kΩ. Otherwise, a terminating resistor must
be used with the LED. Suggested LED connection dia-
grams simplifying the board design are shown in Figure
5 (standard) and Figure 6 (advanced).
The value of the series resistor (R
to ensure sufficient illumination of the LED. R
pendent on the rating of the LED.
The LED pins are totem-pole configuration and should
not be tied together.
Table 7. Standard LED Mode and Advanced LED
Mode
S H E E T
Standard LED Pin
LEDSPD[1]
LEDSPD[0]
LEDDPX
LEDLNK
LEDRX
LEDTX
Mode Pins
Advanced LED Pin
L
LEDTXA/LEDTXB
LEDBTA/LEDBTB
) should be selected
not available
see Table 8
see Table 9
LEDLNK
22235K
L
is de-