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T7256A

Compliance with the New ETSI PSD Requirement

Agere -> LSI Corporation 

T7256 Single-Chip NT1 (SCNT1) Transceiver

Data Sheet

January 1998

S/T-Interface Frame Structure (continued)

The T7256 supports multiframing on the S/T-interface

in conjunction with an external microprocessor that is

used to enable multiframing and transmit and receive

S- and Q-channel messages. When multiframing is

enabled, the M bit in the NT-to-TE direction is set to a

one every 20 frames and the FA bit is set to one every

five frames. The TE recognizes these states and, in

returned frames immediately corresponding to those in

which the NT set the FA bit, replaces the FA bit it sends

to the NT with a Q bit (Q1 through Q4). Q1 is returned

for each frame in which both the M and FA bits were set

to one by the NT, with Q2 through Q4 following at five-

frame intervals. (See Figure 8.)

The S-bit position in the NT-to-TE direction is divided

into five 4-bit subchannels during multiframing: SC1—

SC5. Message sets for subchannels SC3—SC5 are

not currently defined, and a message set for SC2 is

defined only in ANSI T1.605, but not ITU I.430 (see the

S/T-Interface Multiframing Controller Description sec-

tion for more details). Figure 8 indicates the location of

the various S-subchannel bits during multiframing.

20-FRAME MULTIFRAME

19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2

(NT TO TE)

FA = 1

FA = 1

FA = 1

FA = 1

FA = 1

M BIT = 1

IN FRAME #1

S BITS OCCUR IN BIT 37

OF EACH NT-TO-TE FRAME.

S-SUBCHANNEL #1 BITS—

SC11, SC12, SC13, AND SC14

APPEAR IN FRAMES 1, 6, 11,

AND 16.

MARKS START

OF MULTIFRAME

S-SUBCHANNEL #2 BITS—

SC21, SC22, SC23, AND SC24

(TE TO NT)

FA = Q1

FA = Q2

FA = Q3

FA = Q4

FA = Q1 APPEAR IN FRAMES 2, 7, 12,

19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 AND 17.

THE TE-TO-NT TRANSMISSION

HAS A NOMINAL 2-bit DELAY

RELATIVE TO THE NT-TO-TE FRAMES.

Q BITS OCCUR EVERY FIVE FRAMES. THERE ARE

FOUR Q BITS PER MULTIFRAME IN THE FA BIT

POSITION (BIT 14) OF FRAMES 1, 6, 11, AND 16.

5-2481.b (C)

Figure 8. Multiframing—S Subchannels and Q Subchannels

16

Lucent Technologies Inc.

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