T7256 Agere Systems, T7256 Datasheet - Page 21

• Manufacturer Part Number: T7256
• Description: (T7234 - T7256) Compliance
• Manufacturer: Agere Systems

Lucent Technologies Inc.
February 1998
eoc State Machine Description
The following list shows the eight eoc states defined in
ANSI T1.601 and ETSI ETR 080. The bit pattern below
represents the state of U-interface overhead bits
eoci1—eoci8, respectively (see Table 2).
The T7234 automatically handles the eoc channel pro-
cessing per the ANSI and ETSI standards.
ANSI Maintenance Control Description
The ANSI maintenance controller of the T7234 can
operate in fully automatic or in fully manual mode.
Automatic mode can be used in applications where
01010000—Operate 2B+D loopback.
01010001—Operate B1 channel loopback.
01010010—Operate B2 channel loopback.
01010011—Request corrupt CRC.
01010100—Notify of corrupted CRC.
11111111—Return to normal (default).
00000000—Hold state.
10101010—Unable to comply.
T7234 Single-Chip NT1 (SCNT1) Euro-LITE Transceiver
autonomous control of the metallic loop termination
(MLT) maintenance is desired. The MLT capability
implemented with the Lucent LH1465AB and an opto-
coupler provides a dc signature, sealing current sink,
and maintenance pulse-level translation for the testing
facilities. Maintenance pulses from the U-interface MLT
circuit are received by the OPTOIN pin and digitally fil-
tered for 20 ms. The device decodes these pulses
according to ANSI maintenance state machine require-
ments and responds to each request automatically.
For example, the T7234 will place itself in the quiet
mode if six pulses are received from the MLT circuitry.
Manual mode can be used in applications where an
external maintenance decoder is used to drive the
RESET and ILOSS pins of the T7234. In this mode, the
RESET pin places the device in quiet mode and the
ILOSS pin controls SN1 tone transmission.
Board-Level Testing
For board-level testing during manufacturing, the
HIGHZ pin 3-states all digital outputs.
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