TLK2201JR

1.0 Gb to 1.6 Gb SMALL FORMFACTOR ETHERNET TRANSCEIVER

SCAS652F − AUGUST 2000 − REVISED MAY 2007

8

POST OFFICE BOX 655303

detailed description (continued)

testability

The loopback function provides for at-speed testing of the transmit/receive portions of the circuitry. The enable

function allows for all circuitry to be disabled so that an Iddq test can be performed. The PRBS function also

allows for a BIST( built-in self test). The terminal setting, TESTEN high, enables the test mode. The terminal

TESTEN has an internal pulldown resistor, so it defaults to normal operation. The TESTEN is only used for

factory testing, and is not intended for the end-user.

loopback testing

The transceiver can provide a self-test function by enabling (LOOPEN to high level) the internal loopback path.

Enabling this function cause serial transmitted data to be routed internally to the receiver. The parallel data

output can be compared to the parallel input data for functional verification. (The external differential output is

held in a high-impedance state during the loopback testing.)

enable function

When held low, enable disables all quiescent power in both the analog and digital circuitry. This allows an

ultralow-power idle state when the link is not active.

PRBS function

enabled. A PRBS is generated and fed into the 10-bit parallel transmitter input bus. Data from the normal parallel

input source is ignored during PRBS test mode. The PBRS pattern is then fed through the transmit circuitry as

if it were normal data and sent out to the transmitter. The output can be sent to a (BERT) bit error rate tester

or to the receiver of another TLK2201. Since the PRBS is not really random and is really a predetermined

sequence of ones and zeros, the data can be captured and checked for errors by a BERT. The TLK2201 also

has a built-in BERT function on the receiver side that is enabled by PRBSEN. It can receive a PRBS pattern

and check for errors, and then reports the errors by forcing the SYNC/PASS terminal low. When PRBS is

enabled, RBCMODE is ignored. MODESEL must be low for the PRBS verifier to function correctly. The PRBS

testing supports two modes (normal and latched), which are controlled by the SYNC enable input. When

SYNCEN is low, the result of the PRBS bit error rate test is passed to the SYNC/PASS terminal. When SYNCEN

is high the result of the PRBS verification is latched on the SYNC/PASS output (i.e., a single failure forces

SYNC/PASS to remain low).