DS2155 datasheet(170/238 Pages) DALLAS

170 / 238 page

DS2155

170 of 238

26.

BERT FUNCTION

The BERT block can generate and detect pseudorandom and repeating bit patterns. It is used to test and

stress data communication links, and it is capable of generating and detecting the following patterns:

The pseudorandom patterns 2E7, 2E11, 2E15, and QRSS

A repetitive pattern from 1 to 32 bits in length

Alternating (16-bit) words that flip every 1 to 256 words

Daly pattern

The BERT receiver has a 32-bit bit counter and a 24-bit error counter. The BERT receiver reports three

events: a change in receive synchronizer status, a bit error being detected, and if either the bit counter or

the error counter overflows. Each of these events can be masked within the BERT function through the

BERT control register 1 (BC1). If the software detects that the BERT has reported an event, then the

software must read the BERT information register (BIR) to determine which event(s) has occurred. To

activate the BERT block, the host must configure the BERT mux through the BIC register.

26.1 Status

SR9 contains the status information on the BERT function. The host can be alerted through this register

when there is a BERT change-of-state. A major change-of-state is defined as either a change in the

receive synchronization (i.e., the BERT has gone into or out of receive synchronization), a bit error has

been detected, or an overflow has occurred in either the bit counter or the error counter. The host must

read status register 9 (SR9) to determine the change-of-state.

26.2 Mapping

The BERT function can be assigned to the network direction or backplane direction through the direction

control bit in the BIC register (BIC.1). See Figure 26-1 and Figure 26-2. The BERT also can be assigned

on a per-channel basis. The BERT transmit control selector (BTCS) and BERT receive control selector

(BRCS) bits of the per-channel pointer register (PCPR) are used to map the BERT function into time slots

of the transmit and receive data streams. In T1 mode, the user can enable mapping into the F-bit position

for the transmit and receive directions through the RFUS and TFUS bits in the BERT interface control

(BIC) register.

DS2155 Datasheet(PDF) 170 Page - Dallas Semiconductor