ds26518 Maxim Integrated Products, Inc., ds26518 Datasheet - Page 87

• Manufacturer Part Number: ds26518
• Description: 8-port T1/e1/j1 Transceiver
• Manufacturer: Maxim Integrated Products, Inc.

Figure 9-22. Receive LIU Termination Options
The device couples to the receive E1 or T1 twisted pair (or coaxial cable in 75: E1 applications) via a 1:1 or 2:1
transformer. See
Receive sensitivity is configurable by setting the appropriate RSMS[1:0] bits (LRCR).
The DS26518 uses a digital clock recovery system. The resultant E1, T1 or J1 clock derived from MCLK is
multiplied by 16 via an internal PLL and fed to the clock recovery system. The clock recovery system uses the
clock from the PLL circuit to form a 16 times oversampler, which is used to recover the clock and data. This
oversampling technique offers outstanding performance to meet jitter tolerance specifications shown in
Figure
Normally, the clock that is output at the RCLKn pin is the recovered clock from the E1 AMI/HDB3 or T1 AMI/B8ZS
waveform presented at the RTIPn and RRINGn inputs. If the jitter attenuator (LTRCR) is placed in the receive path
(as is the case in most applications), the jitter attenuator restores the RCLKn to an approximate 50% duty cycle. If
the jitter attenuator is either placed in the transmit path or is disabled, the RCLKn output can exhibit slightly shorter
high cycles of the clock. This is due to the highly over-sampled digital clock recovery circuitry. See
more details. When no signal is present at RTIPn and RRINGn, a receive carrier loss (RCL) condition will occur
and the RCLKn will be derived from the MCLKT1 or MCLKE1 source (depending on the configuration).
9.12.3.2
The DS26518 will report the signal strength at RTIPn and RRINGn in approximately 2.5dB increments via RSL[3:0]
located in the LIU Receive Signal Level Register (LRSL). This feature is helpful when trouble shooting line
performance problems.
9.12.3.3
The DS26518 can receive a 2.048MHz square-wave synchronization clock as specified in Section 10 of ITU-T
G.703. To use this mode, set the receive G.703 clock bit (RG703) found in the LIU Receive Control Register
(LRCR.7).
9-25.
Receive Level Indicator
Receive G.703 Section 10 Synchronization Signal
Table 9-40
RECEIVE LIU
R
T
for transformer details.
R
T
RRINGn
RTIPn
LRISMR.RIMPON
87 of 286
TFR
1:1
DS26518 8-Port T1/E1/J1 Transceiver
Rx LINE
Table 13-3
for