TMPR28051 datasheet(24/90 Pages) AGERE

24 / 90 page

Data Sheet

TMPR28051 STS-1/AU-3 (STM-0) Mapper

August 1999

Lucent Technologies Inc.

Nomenclature Assumptions

The mapping methods (VT1.5, VT2, and VT Group in

ANSI nomenclature; TU-11, TU-12, and TUG-2 in ITU

nomenclature) are analogous, and for the rest of this

document will be referred to as VT1.5, VT2, or VT

Group. STS-1 and AU-3 are also analogous with a few

minor differences.

For the remainder of this document, the 51.84 Mbits/s

signals are referred to as STS-1.

DS1/E1 to STS-1 Block Descriptions

In the descriptions of the block diagram of Figure 1,

some of the control bits exist for each of the DS1/E1 or

VT signals.

Upon start-up, the device will set all of the input data

types (DS1 or E1) based on the level of the DS1_E1N

pin (pin 102). DS1_E1N controls the value transmitted

in the unused overhead bytes and the value of the

transmitted spare bits (SS) in the H1 byte. If this pin is

high, then all of the VT Groups are populated with DS1

signals. If this pin is low, then all of the VT Groups are

populated with E1 signals.

This default selection can be overridden by setting

TOVERRIDE and ROVERRIDE bits in registers 0x88

(bit 0) and 0x89 (bit 0), respectively. The seven VT

Groups can then be individually programmed to carry

either DS1 (TVTG-1 . . . 7 = 1, RVTG-1 . . . 7 = 1) or E1

(TVTG-1 . . . 7 = 0, RVTG-1 . . . 7 = 0) signals.

LOC and AIS Monitor

The incoming DS1/E1 signal is first checked for loss of

clock (LOC). LOC is reported to the microprocessor via

the DS1/E1LOC[1:21] and DS1LOC[22:28] bit

(LOC = 1, 0 otherwise) in registers 0x17—0x32 (bit 6)

and also via the AISLOCCOM composite bit in register

0x05 (bit 1). If LOC is present, the device inserts DS1/

E1 AIS towards the STS-1 using the blue signal clock.

The incoming DS1/E1 data (RDATA[28:1]) is

retimed immediately by the associated DS1/E1 clock

(RCLK[28:1]). The edge of the clock that is used to

retime the data is user-provisionable at the device level

to either the rising edge (RXDS1EDGE = 1) in register

0x02 (bit 1) or falling edge (RXDS1EDGE = 0) in regis-

ter 0x02 (bit 1).

After being retimed, the incoming data stream is

checked for AIS. The device will declare AIS if the input

data is at logic 1 for 3 ms. The device will withstand up

to eight errors in the 3 ms period. AIS is reported to the

microprocessor via the AISLOCCOM composite bit in

DS1/E1AIS[1:21] and DS1AIS[22:28] bits in registers

0x17—0x32 (bit 7).

The blue signal clock input signal to the device can be

at the exact DS1/E1 rate (1.544/2.048 MHz) or at 16

times the DS1/E1 rate (24.704/32.768 MHz), with a tol-

erance of 32 ppm or 50 ppm for DS1 or E1, respec-

tively. This allows users of the Lucent Technologies

T7698FL3/T7693 devices to reuse the XCLK on the

board. The TMPR28051 is provisioned to accept the

exact DS1 rate by default (BLUECLKSEL = 0 in bit 2 of

divide-by-16 function (BLUECLKSEL = 1 in bit 2 of reg-

ister 0x00). The duty cycle of the clock can be 45%/

55% because the data is retimed internally in the

device. The duty cycle requires a much tighter toler-

ance when used for XCLK as described earlier.

DS1/E1 Loopback Select Logic

The first stage after retiming the signal into the device

is selection of the externally received DS1/E1

(DS1/E1LB[1:21] or DS1LB[22:28] = 0) or the looped

back DS1/E1 (DS1/E1LB[1:21] or DS1LB[22:28] = 1).

This selection is provisionable per DS1/E1 input in reg-

isters 0x17—0x32 (bit 5).

Input Select Logic

Once the DS1/E1 data sources have been selected,

the DS1/E1 for each VT tributary is selected. This

selection requires 5 bits per slot to determine

which DS1/E1 input to use by provisioning

DS1/E1INS[4:0]_[1:21] or DS1INS[4:0]_[22:28] bits in

registers 0x17—0x32 (bits 4 through 0). The range

[1:28] following the _ refers to the target VT #. Refer to

Table 8 on page 15 and Table 10 on page 15 for details

on the VT locations within the SPE.

The numbering scheme for the five provisioned bits

ranges from 00001 to 11100 where the binary value of

the 5 bits corresponds to the DS1/E1 input. For

instance, the value 00001 corresponds to selecting

DS1/E1 #1.

The unused value of 00000 results in VT unequipped

being transmitted. This is the default value for all the

VT slots at powerup. VT unequipped has a valid

pointer and all-zero payload.

The unused values of 11101—11110 will cause AIS-V

to be inserted for that VT slot.

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