T7264 datasheet(4/54 Pages) AGERE

4 / 54 page

Lucent Technologies Inc.

Data Sheet

April 1998

T7264 U-Interface 2B1Q Transceiver

Pin Information (continued)

Table 2. Pin Descriptions

Symbol

Type

Name/Function

K2 Transmit Data Input. Serial data input passing transmit data across K2 in-

terface at 512 kbits/s. Latched on falling edge of C clock.

MTC

Master Timing Clock. 8 kHz clock input. In LT mode (MODE0 = 1), all clocks

except CKOUT in the 15.36 MHz and 7.68 MHz modes are locked to this input

clock. In the NT mode (MODE0 = 0), this input is not used.

512 kbits/s K2 Bit Clock Output. Synchronized to F. Defines K2 bit period (ris-

ing edge to rising edge).

K2 Receive Data Output. Serial data output passing receive data across K2 in-

terface at 512 kbits/s. Changes on the rising edge of C clock.

8 kHz Clock Output. Defines K2 frame (rising edge to rising edge). In LT mode

(MODE0 = 1), this clock is locked to MTC at 0

° phase shift with ±65 ns of jitter

(for jitter-free MTC). In NT mode (MODE0 = 0), this clock is derived from the

U-interface signal.

6, 17

VDDD

+5 V Supply for Digital Circuits. Internally connected together.

RESET

Reset (Active-Low). Asynchronous Schmitt trigger input. This pin maintains

the transceiver in reset indefinitely without the need to access the K2 interface.

It must be held low for three consecutive F clock periods for active or idle mode

or 1.5 ms after power on. After power-on reset or idle mode reset, an additional

1.0 ms is required before the device is fully functional. RESET overrides all other

transceiver control signals, halts loop transmission, clears the transceiver adap-

tive filter coefficients, and resets the phase-locked loop. After a reset, the next

activation is a cold start. Unlike afrst (software reset via the K2 interface), when

this pin is held low, synchronization is lost between F and MTC (LT). After this

pin goes high, F and MTC regain synchronization. All output clocks remain func-

tional during reset.

FFC

Freeze Frequency Control (Active-Low). Asynchronous input. Freeze the

clock frequency control (i.e., the internal state variables of the timing recovery

remain constant). This control is operative in both LT and NT modes. This pin is

latched on the rising edge of every RCLKEN.

ILOSS

Insertion Loss Test (Active-Low). NT ONLY. When enabled, the transmitter

continuously transmits the sequence SN1. The receiver remains reset. The

transceiver performs a reset when this pin returns to its inactive state. ILOSS is

latched on the rising edge of F. Leave this pin unconnected or tied to VDD in LT

mode.

10, 11

MODE[0:1]

Mode 0 and 1. Two-pin field selecting chip mode:

MODE0

Action

Configure for chip being used on the NT end of loop.

Configure for chip being used on the LT end of loop.

MODE1

Action

Disables autoreporting of nebe to febe.

Enables autoreporting of nebe to febe.

12, 22,

27, 44

GNDD

Ground Supply for Digital Circuits. Internally connected together.

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