DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
CCR4: COMMON CONTROL REGISTER 4 (Address = A8 Hex)
(MSB)
(LSB)
RLB
LLB
LIAIS
TCM4
TCM3
TCM2
TCM1
TCM0
SYMBOL POSITION
NAME AND DESCRIPTION
Remote Loopback.
0 = loopback disabled
1 = loopback enabled
Local Loopback.
RLB
CCR4.7
LLB
CCR4.6
0 = loopback disabled
1 = loopback enabled
Line Interface AIS Generation Enable.
0 = allow normal data from TPOSI/TNEGI to be transmitted at TTIP and
TRING
LIAIS
TCM4
CCR4.5
CCR4.4
1 = force unframed all ones to be transmitted at TTIP and TRING at the
MCLK rate
Transmit Channel Monitor Bit 4. MSB of a channel decode that
determines which transmit channel data will appear in the TDS0M
register. See Section 8 for details.
TCM3
TCM2
TCM1
TCM0
CCR4.3
CCR4.2
CCR4.1
CCR4.0
Transmit Channel Monitor Bit 3.
Transmit Channel Monitor Bit 2.
Transmit Channel Monitor Bit 1.
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 Figure 2-1 for more details.
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 Figure 2-1 for more details.
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