DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
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CCR4: COMMON CONTROL REGISTER 4 (Address = A8 Hex)
(MSB)
(LSB)
RLB LLB LIAIS TCM4 TCM3 TCM2 TCM1 TCM0
SYMBOL
POSITION
NAME AND DESCRIPTION
RLB CCR4.7
Remote Loopback.
0 = loopback disabled
1 = loopback enabled
LLB CCR4.6
Local Loopback.
0 = loopback disabled
1 = loopback enabled
LIAIS CCR4.5
Line Interface AIS Generation Enable.
0 = allow normal data from TPOSI/TNEGI to be transmitted at TTIP and
TRING
1 = force unframed all ones to be transmitted at TTIP and TRING at the
MCLK rate
TCM4 CCR4.4
Transmit Channel Monitor Bit 4.
MSB of a channel decode that
determines which transmit channel data will appear in the TDS0M
register. See Section
for details.
TCM3 CCR4.3
Transmit Channel Monitor Bit 3.
TCM2 CCR4.2
Transmit Channel Monitor Bit 2.
TCM1 CCR4.1
Transmit Channel Monitor Bit 1.
TCM0 CCR4.0
Transmit Channel Monitor Bit 0. LSB of the channel decode.
5.5.
Remote Loopback
When CCR4.7 is set to a one, the SCT will be forced into remote loopback (RLB). In this loopback, data
input via the RPOSI and RNEGI pins will be transmitted back to the TPOSO and TNEGO pins. Data will
continue to pass through the receive-side framer of the SCT as it would normally and the data from the
transmit-side formatter will be ignored. Please see
5.6.
Local Loopback
When CCR4.6 is set to one, the SCT will be forced into local loopback (LLB). In this loopback, data will
continue to be transmitted as normal through the transmit side of the SCT. Data being received at RTIP
and RRING will be replaced with the data being transmitted. Data in this loopback will pass through the
jitter attenuator. Please see
for more details.