DS26521 datasheet(34/258 Pages) MAXIM

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DS26521 Single T1/E1/J1 Transceiver

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8.8.1.4 Receiving Mapped T1 Channels from a 2.048MHz Backplane

Setting the TSCLKM bit (TIOCR.4) enables the transmit elastic store to operate with a 2.048MHz backplane (32

time slots/frame). In this mode the user can choose which of the backplane channels on TSER will be mapped into

the T1 data stream by programming the Transmit Blank Channel Select registers (TBCS1:TBCS4). A logic 1 in the

associated bit location forces the transmit elastic store to ignore backplane data for that channel. Typically the user

will want to program eight channels to be ignored. The default (power-up) configuration ignores channels 25 to 32,

so that the first 24 backplane channels are mapped into the T1 transmit data stream.

For example, if the user desired to transmit data from the 2.048MHz backplane channels 2 to 16 and 18 to 26, the

TBCS1:TBCS4 registers should be programmed as follows:

TBCS1 = 01h :: ignore backplane channel 1 ::

TBCS2 = 00h

TBCS3 = 01h :: ignore backplane channel 17 ::

TBCS4 = FCh :: ignore backplane channels 27 to 32 ::

8.8.1.5 Mapping T1 Channels onto a 2.048MHz Backplane

Setting the RSCLKM bit (RIOCR.4) enables the receive elastic store to operate with a 2.048MHz backplane (32

time slots/frame). In this mode the user can choose which of the backplane channels on RSER receive the T1 data

by programming the Receive Blank Channel Select registers (RBCS1:RBCS4). A logic 1 in the associated bit

location forces RSER high for that backplane channel. Typically the user will want to program eight channels to be

blanked. The default (power-up) configuration blanks channels 25 to 32, so that the 24 T1 channels are mapped

into the first 24 channels of the 2.048MHz backplane. If the user chooses to blank channel 1 (TS0) by setting

RBCS1.0 = 1, the F-bit will be passed into the MSB of TS0 on RSER.

For example, if:

RBCS1 = 01h

RBCS2 = 00h

RBCS3 = 01h

RBCS4 = FCh

Then on RSER:

Channel 1 (MSB) = F-bit

Channel 1 (bits 1 to 7) = all ones

Channels 2 to 16 = T1 channels 1 to 15

Channel 17 = all ones

Channels 18 to 26 = T1 channels 16 to 24

Channels 27 to 32 = all ones

Note that when two or more sequential channels are chosen to be blanked, the receive slip zone select bit should

be set to 0. If the blank channels are distributed (such as 1, 5, 9, 13, 17, 21, 25, 29), the RSZS bit can be set to 1,

which can provide a lower occurrence of slips in certain applications.

If the two-frame elastic buffer either fills or empties, a controlled slip occurs. If the buffer empties, a full frame of

data is repeated at RSER and the RLS4.5 and RLS4.6 bits are set to 1. If the buffer fills, a full frame of data is

deleted and the RLS4.5 and RLS4.7 bits are set to 1.

8.8.1.6 Receiving Mapped E1 Transmit Channels from a 1.544MHz Backplane

The user can use the TSCLKM bit in TIOCR.4 to enable the transmit elastic store to operate with a 1.544MHz

backplane (24 channels / frame + F-bit). In this mode the user can choose which of the E1 time slots will have all-

ones data inserted by programming the Transmit Blank Channel Select registers (TBCS1:TBCS4). A logic 1 in the

associated bit location causes the elastic store to force all ones at the outgoing E1 data for that channel. Typically

the user will want to program eight channels to be blanked. The default (power-up) configuration blanks channels

25 to 32, so that the first 24 E1 channels are mapped from the 24 channels of the 1.544MHz backplane.

DS26521 Datasheet(PDF) 34 Page - Maxim Integrated Products

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