CP2201 datasheet(89/108 Pages) SILABS

89 / 108 page

CP2200/1

Rev. 1.0

15.3. Loopback Mode

Loopback Mode provides the ability to transfer data from the physical layer’s output directly to it’s input to aid in

system debugging. When PHYCN.3 is set to ‘1’, transmit data is looped back to the receiver via an internal analog

path. The transmit drivers and receive input circuitry are bypassed, isolating the device from the network. This

prevents network traffic from affecting the result of any system self-tests and guarantees a collision-free

environment.

15.4. Link Integrity Function

The Link Integrity function provides the ability to detect and respond to a 10 BASE-T link failure. When such a

failure is detected, the transmitter and receiver are automatically disabled, and the state of the link is reported in

LINKSTA (PHYCN.0). The host can disable the link integrity function by clearing LINKINT (PHYCF.6) to ‘0’. When

the link integrity function is disabled, the physical layer will operate regardless of the presence of link pulses.

15.5. Receiver Smart Squelch and Automatic Polarity Correction

The physical layer receiver can detect and correct for noise or incorrect polarity of the received signal. If the

receiver Smart Squelch feature is enabled by setting SMSQ (PHYCF.7) to ‘1’, the receiver circuitry performs a

combination of amplitude and timing measurements (in accordance with IEEE 802.3) to determine the validity of

received data. This prevents noise from falsely triggering the receiver in the absence of valid data.

Automatic polarity correction can automatically detect and correct the polarity of the received data to compensate

for a wiring error at either end of the 10 BASE-T cable. When automatic polarity correction is enabled by setting

AUTOPOL (PHYCF.1) to ‘1’, the polarity of the receive data is indicated in POLREV (PHYCN.1). When automatic

polarity detection is disabled, the polarity of the receive data can be manually reversed by setting REVPOL

(PHYCF.0) to ‘1’.

15.6. Transmitter Jabber Function

Provides the ability to automatically disable the transmitter if software attempts to transmit a packet longer than the

maximum allowed packet length (per IEEE 802.3). The host processor will be notified via the Jabber Detected

Interrupt if a jabber condition is automatically handled by the hardware. Enabling the jabber function is

recommended to ensure that the embedded system using the CP2200/1 for Ethernet communication does not

generate a jabber condition on the wire.

CP2201 Datasheet(PDF) 89 Page - Silicon Laboratories