Rainbow Electronics DS2141A User Manual

Page 12

DS2141A

021997 12/35

SEFE

RIR.2

Severely Errored Framing Event. Set when 2 out of 6 framing bits are
received in error.

B8ZS

RIR.1

B8ZS Code Word Detect. Set when a B8ZS code word is detected at
RPOS and RNEG independent of whether the B8ZS mode is selected or
not via CCR2.2.

FBE

RIR.0

Frame Bit Error. Set when a Ft (D4) or FPS (ESF) framing bit is received in
error.

Note: If the transmit elastic store slips, both RIR.4 and RIR.3 will be set.

SR1: STATUS REGISTER 1 (20h)

(MSB)

(LSB)

LUP

LDN

LOTC

SLIP

RBL

RYEL

RCL

RLOS

SYMBOL

POSITION

NAME AND DESCRIPTION

LUP

SR1.7

Loop Up Code Detected. Set when the repeating ...00001... loop up code
is being received.

LDN

SR1.6

Loop Down Code Detected. Set when the repeating ...001... loop down
code is being received.

LOTC

SR1.5

Loss of Transmit Clock. Set when the TCLK pin has not transitioned for
one channel time (or 5.2

s). Will force pin–34 high if enabled via CCR1.6.

Based on RCLK.

SLIP

SR1.4

Elastic Store Slip Occurrence. Set when the elastic store has either re-
peated or deleted a frame of data.

RBL

SR1.3

Receive Blue Alarm. Set when an all 1’s code is received at RPOS and
RNEG.

RYEL

SR1.2

Receive Yellow Alarm. Set when a yellow alarm is received at RPOS and
RNEG.

RCL

SR1.1

Receive Carrier Loss. Set when 192 consecutive 0s have been detected
at RPOS and RNEG.

RLOS

SR1.0

Receive Loss of Sync. Set when the device is not synchronized to the
receive T1 stream.

LOOP UP/DOWN CODE DETECTION

Bits SR1.7 and SR1.6 will indicate when either the stan-
dard “loop up” or “loop down” codes are being received
by the DS2141A. When a loop up code has been re-
ceived for 5 seconds, the CPE is expected to loop the
recovered data (without correcting BPVs) back to the
source. The loop down code indicates that the loopback
should be discontinued. See the AT&T publication TR
62411 for more details. The DS2141A will detect the
loop up/down codes in both framed and unframed cir-

cumstances with bit error rates as high as 10–

. The

loop code detector has a nominal integration period of
48 ms. Hence, after about 48 ms of receiving either
code, the proper status bit will be set to a 1. After this
initial indication, it is recommend that the software poll
the DS2141A every 100 ms to 500 ms until five seconds
has elapsed to insure that the code is continuously pres-
ent. Once five seconds has passed, the line interface
should be taken into or out of loopback.