Rainbow Electronics DS2151Q - Manual (Page 17)

DS2151Q
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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 DS2151Q. When a loop up code has been
received 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 DS2151Q will detect the
loop up/down codes in both framed and unframed cir-
cumstances with bit error rates as high as 10**–2. 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 one. After this
initial indication, it is recommended that the software
poll the DS2151Q every 100 ms to 500 ms until
5 seconds has elapsed to insure that the code is contin-
uously present. Once 5 seconds has passed, the
DS2151Q should be taken into or out of loopback via the
Remote Loopback (RLB) bit in CCR1.
SR2: STATUS REGISTER 2 (Address=21 Hex)
(MSB) (LSB)
RMF TMF SEC RFDL TFDL RMTCH RAF –
SYMBOL POSITION NAME AND DESCRIPTION
RMF SR2.7 Receive Multiframe. Set on receive multiframe boundaries.
TMF SR2.6 Transmit Multiframe. Set on transmit multiframe boundaries.
SEC SR2.5 One Second Timer. Set on increments of one second based on RCLK; will
be set in increments of 999 ms, 999 ms, and 1002 ms every 3 seconds.
RFDL SR2.4 Receive FDL Buffer Full. Set when the receive FDL buffer (RFDL) fills to
capacity (8–bits).
TFDL SR2.3 Transmit FDL Buffer Empty. Set when the transmit FDL buffer (TFDL)
empties.
RMTCH SR2.2 Receive FDL Match Occurrence. Set when the RFDL matches either
RFDLM1 or RFDLM2.
RAF SR2.1 Receive FDL Abort. Set when eight consecutive one’s are received in the
FDL.
– SR2.0 Not Assigned. Should be set to zero when written.
IMR1: INTERRUPT MASK REGISTER 1 (Address=7F Hex)
(MSB) (LSB)
LUP LDN LOTC SLIP RBL RYEL RCL RLOS
SYMBOL POSITION NAME AND DESCRIPTION
LUP IMR1.7 Loop Up Code Detected.
0=interrupt masked
1=interrupt enabled
LDN IMR1.6 Loop Down Code Detected.
0=interrupt masked
1=interrupt enabled
LOTC IMR1.5 Loss of Transmit Clock.
0=interrupt masked
1=interrupt enabled