DS26503 datasheet(79/123 Pages) DALLAS

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DS26503 T1/E1/J1 BITS Element

79 of 123

13.2.2 Receive G.703 Section 10 Synchronization Signal

The DS26503 can receive a 2.048MHz square-wave synchronization clock as specified in Section 10 of

ITU G.703. To use the DS26503 in this mode, set the mode configuration bits in the Mode Configuration

13.2.3 Monitor Mode

Monitor applications in both E1 and T1 require various flat gain settings for the receive-side circuitry.

The DS26503 can be programmed to support these applications via the monitor mode control bits MM1

and MM0 in the LIC3 register.

Figure 13-2. Typical Monitor Application

13.3 LIU Transmitter

The DS26503 uses a phase-lock loop along with a precision digital-to-analog converter (DAC) to create

the waveforms that are transmitted onto the E1 or T1 line. The waveforms created by the DS26503 meet

the latest ETSI, ITU, ANSI, and AT&T specifications. The waveform that is to be generated is set by the

transmit mode bits (TMODE[3:0]) in the MCREG register, as well as the L2/L1/L0 bits in register LIC1

if applicable.

ITU specification G.703 requires an accuracy of ±50ppm for both T1 and E1. TR62411 and ANSI specs

require an accuracy of ±32ppm for T1 interfaces. The transmit clock can be sourced from the recovered

clock (RCLK), the pre-scaled MCLK, the TCLK pin or the TX PLL. See the TX PLL clock mux diagram

in Figure 3-3. Due to the nature of the design of the transmitter in the DS26503, very little jitter (less than

0.005 UIP-P broadband from 10Hz to 100kHz) is added to the jitter present on the selected transmit clock

source. Also, the waveforms created are independent of the duty cycle of TCLK. The transmitter in the

DS26503 couples to the transmit twisted pair (or coaxial cable in some applications) via a 1:2 step-up

transformer. For the device to create the proper waveforms, the transformer used must meet the

specifications listed in Table 13-1. The DS26503 has the option of using software-selectable transmit

termination.

PRIMARY

T1/E1 TERMINATING

DEVICE

MONITOR

PORT JACK

T1/E1 LINE

DS26503

SECONDARY T1/E1

TERMINATING

DEVICE

DS26503 Datasheet(PDF) 79 Page - Dallas Semiconductor