DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
6.1. CRC4 Sync Counter
The CRC4 Sync Counter increments each time the 8ms CRC4 multiframe search times out. The counter
is cleared when the framer has successfully obtained synchronization at the CRC4 level. The counter can
also be cleared by disabling the CRC4 mode (CCR1.0 = 0). This counter is useful for determining the
amount of time the framer has been searching for synchronization at the CRC4 level. ITU G.706 suggests
that if synchronization at the CRC4 level cannot be obtained within 400ms, then the search should be
abandoned and proper action taken. The CRC4 Sync Counter will roll over.
SR1: STATUS REGISTER 1 (Address = 06 Hex)
(MSB)
(LSB)
RSA1
RDMA
RSA0
RSLIP
RUA1
RRA
RCL
RLOS
SYMBOL POSITION
NAME AND DESCRIPTION
Receive Signaling All Ones/Signaling Change. Set when the contents
of time slot 16 contain less than three zeros over 16 consecutive frames.
This alarm is not disabled in the CCS signaling mode. Both RSA1 and
RSA0 will be set if a change in signaling is detected.
Receive Distant MF Alarm. Set when bit 6 of time slot 16 in frame 0
has been set for two consecutive multiframes. This alarm is not disabled
in the CCS signaling mode.
RSA1
SR1.7
RDMA
RSA0
SR1.6
SR1.5
Receive Signaling All Zeros/Signaling Change. Set when over a full
MF, time slot 16 contains all zeros. Both RSA1 and RSA0 will be set if a
change in signaling is detected.
Receive-Side Elastic Store Slip. Set when the elastic store has either
repeated or deleted a frame of data.
RSLIP
RUA1
RRA
SR1.4
SR1.3
SR1.2
Receive Unframed All Ones. Set when an unframed all ones code is
received at RPOSI and RNEGI.
Receive Remote Alarm. Set when a remote alarm is received at RPOSI
and RNEGI.
Receive Carrier Loss. Set when 255 (or 2048 if CCR3.0 = 1)
consecutive zeros have been detected at RTIP and RRING. (Note: a
receiver carrier loss based on data received at RPOSI and RNEGI is
available in the HSR register)
Receive Loss of Sync. Set when the device is not synchronized to the
receive E1 stream.
RCL
SR1.1
SR1.0
RLOS
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