DS26401 datasheet(80/309 Pages) DALLAS

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DS26401 Octal T1/E1/J1 Framer

8.14.1 Mapping T1 Channels Onto a 2.048MHz Backplane

Setting the RSCLKM bit in 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 (RBCS1–4). A logic 1 in the associated bit location

forces RSER high for that backplane channel. Typically, the user wants to program 8 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, then

the F-bit is 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 1–7) = all ones

Channels 2–16 = T1 channels 1–15

Channel 17 = all ones

Channels 18–26 = T1 channels 16–24

Channels 27–32 = all ones

RBCS1, RBCS2, RBCS3, RBCS4

Receive Blank Channel Select Registers

0C0h, 0C1h, 0C2h, 0C3h [+ (200h x n) : where n = 0 to 7, for Ports 1 to 8]

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

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

can be set to 1, which may provide a lower occurrence of slips in certain applications.

(MSB)

(LSB)

CH8

CH7

CH6

CH5

CH4

CH3

CH2

CH1

RBCS1

CH16

CH15

CH14

CH13

CH12

CH11

CH10

CH9

RBCS2

CH24

CH23

CH22

CH21

CH20

CH19

CH18

CH17

RBCS3

CH32

CH31

CH30

CH29

CH28

CH27

CH26

CH25

RBCS4

Bits 0–7 / Receive Blank Channel Select for Channels 1 to 32 (RBCS1-32).

0 = do not blank this channel (channel data is available on RSER)

1 = RSER is forced to all ones for this channel

DS26401 Datasheet(PDF) 80 Page - Dallas Semiconductor

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