DS26401 datasheet(142/309 Pages) DALLAS

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DS26401 Octal T1/E1/J1 Framer

142

9.19 Programmable In-Band Loop-Code Generator

The DS26401 has the ability to generate and detect a repeating bit pattern from one to eight bits or sixteen bits in

length. This function is available only in T1 mode. To transmit a pattern, the user will load the pattern to be sent into

the Transmit Code Definition registers (TCD1&TCD2) and select the proper length of the pattern by setting the TC0

and TC1 bits in Transmit Control Register 4 (TCR4). When generating a 1-, 2-, 4-, 8-, or 16-bit pattern both

transmit code definition registers (TCD1&TCD2) must be filled with the proper code. Generation of a 3, 5, 6 and 7

bit pattern only requires TCD1 to be filled. Once this is accomplished, the pattern will be transmitted as long as the

TLOOP control bit (TCR3.0) is enabled. Normally (unless the transmit formatter is programmed to not insert the F-

bit position) the framer will overwrite the repeating pattern once every 193 bits to allow the F–bit position to be sent.

As an example, to transmit the standard “loop-up” code for Channel Service Units (CSUs), which is a repeating

pattern of ...10000100001..., set TCD1 = 80h, TC0=0, TC1=0, and TCR3.0 = 1.

This register definition is repeated here for convenience.

TCR4

Transmit Control Register 4

186h + (200h x n) : where n = 0 to 7, for Ports 1 to 8

Bit #

Name

TRAIM

TAISM

TC1

TC0

Default

Bits 0 to 1 / Transmit Code Length Definition Bits (TC0 to TC1)

TC1

TC0

LENGTH SELECTED (BITS)

6/3

16/8/4/2/1

Bit 2 / Transmit AIS Mode (TAISM).

Determines the pattern sent when TAIS (TCR1.1) is activated.

0 = transmit normal AIS (unframed all ones) upon activation with TCR1.1

1 = transmit AIS-CI (T1.403) upon activation with TCR1.1

Bit 3 / Transmit RAI Mode (TRAIM).

Determines the pattern sent when TRAI (TCR1.0) is activated in ESF frame

mode only.

0 = transmit normal RAI upon activation with TCR1.0

1 = transmit RAI-CI (T1.403) upon activation with TCR1.0

Bits 4 to 7 / Unused. Must be set = 0 for proper operation.

DS26401 Datasheet(PDF) 142 Page - Dallas Semiconductor