Diagnostics, Figure 1f. prbs output with normal rclk operation – Rainbow Electronics DS3150 User Manual

Page 11

DS3150

11 of 22

DIAGNOSTICS

The DS3150 contains an onboard Pseudo Random Binary Sequence (PRBS) generator and detector. This
function is useful in testing the device at the physical layer. It will generate and detect either a 2

- 1

(T3 or STS-1) or 2

- 1 PRBS according to the ITU O.151 specification. The PRBS pattern generated

and detected by the DS3150 is unframed. In other words, no T3, E3, or STS-1 framing patterns are
inserted in the transmit data stream nor expected in the received data stream. The PRBS generator is
enabled through the TDS0 and TDS1 inputs (Tables 2A and 2B). The PRBS detector is always enabled
and will report its status through the PRBS output if signal EFE = 1. When the PRBS detector is out of
synchronization, the PRBS output will be forced high. When the PRBS detector synchronizes to the
incoming pseudorandom pattern, the PRBS output will go low and then pulse high for each bit detected in
error (Figures 1F and 1G). On the receive side, the recovered data is B3ZS/HDB3 decoded before it is
routed to the PRBS decoder.

The DS3150 also has two internal loopbacks that can be used for testing (Figure 1A). The analog
loopback loops the outgoing transmit waveform back to the receiver. When this loopback is enabled, data
will be transmitted as it normally would be and the incoming data at Rx+ and Rx- is ignored. The remote
loopback loops data from the receive side to the transmit side. When this loopback is enabled, data will
continue to pass through the receive side as it normally would and data at the TPOS and TNEG inputs is
ignored. These two loopbacks are invoked through the LBKS* input (Table 2A).

Figure 1F. PRBS OUTPUT WITH NORMAL RCLK OPERATION

ICE = 0 or 1

Figure 1G. PRBS OUTPUT WITH INVERTED RCLK OPERATION

ICE = Float

PRBS Detector

is Not in Sync

PRBS Detector is in sync; the PRBS

Signal Will Pulse High for Each Bit Error Detected

RCLK

PRBS