MT9074AP datasheet(21/122 Pages) MITEL

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Advance Information

MT9074

Data Link Operation

Data Link Operation in E1 mode

In E1 mode MT9074 has a user deﬁned 4, 8, 12, 16

or 20 kbit/s data link for transport of maintenance

and performance monitoring information across the

PCM 30 link. This channel functions using the Sa bits

(Sa4~Sa8) of the PCM 30 timeslot zero non-frame

alignment

signal

(NFAS).

Since

the

NFAS

transmitted every other frame - a periodicity of 250

microseconds - the aggregate bit rate is a multiple of

4 kb/s. As there are ﬁve Sa bits independently

available for this data link, the bit rate will be 4, 8, 12,

16 or 20 kb/s, depending on the bits selected for the

Data Link (DL).

The Sa bits used for the DL are selected by setting

the appropriate bits, Sa4~Sa8, to one in the Data Link

Select Word (page 01H, address 17H, bits 4-0).

Access to the DL is provided by pins TxDLCLK,

TxDL, RxDLCLK and RxDL, which allow easy

interfacing to an external controller.

Data to be transmit onto the line in the Sa bit position

is clocked in from the TxDL pad (pin 65 in PLCC, pin

62 in MQFP) with the clock TxDLCLK (pin 64 in

PLCC, pin 61 in MQFP). Although the aggregate

clock rate equals the bit rate, it has a nominal pulse

width of 244 ns, and it clocks in the TxDL as if it were

a 2.048 Mb/s data stream. The clock can only be

active during bit times 4 to 0 of the STBUS frame.

The TxDL input signal is clocked into the MT9074 by

the rising edge of TxDLCLK. If bits are selected to be

a part of the DL, all other programmed functions for

those Sa bit positions are overridden.

The RxDLCLK signal (pin 39 in PLCC, pin 20 in

MQFP) is derived from the receive extracted clock

and is aligned with the receive data link output RxDL.

The HDB3 decoded receive data, at 2.048 Mbit/s, is

clocked out of the device on pin RxDL (pin 40 in

PLCC, pin 21 in MQFP). In order to facilitate the

attachment of this data stream to a Data Link

controller, the clock signal RxDLCLK consists of

positive pulses, of nominal width of 244 ns, during

the Sa bit cell times that are selected for the data

link. Again, this selection is made by programming

address 17H of master control page 01H. No DL

data will be lost or repeated when a receive frame

slip occurs. See the AC Electrical Characteristics for

timing requirements.

Data Link Operation in T1 mode

SLC-96 and ESF protocol allow for carrier messages

to be embedded in the overhead bit position. The

MT9074 provides 3 separate means of controlling

these data links. See Data Link and Rx Equalization

Control Word - address 12H, page 1H.

• The data links (transmit and receive) may be

sourced (sunk) from an external controller using

dedicated pins on the MT9074 in T1 mode (enabled

by setting the bit 7 - EDL of the Data link Control

Word).

• Bit - Oriented Messages may be transmit and

received via a dedicated TxBOM register (page 1H,

address 13H) and a RxBOM (page 3H, address

15H). Transmission is enabled by setting bit 6 -

BIOMEn in the Data link Control Word. Bit - oriented

messages may be periodically interrupted (up to

once per second) for a duration of up to 100

milliseconds. This is to accommodate bursts of

message - oriented protocols. See Table 16 for

message structure.

• An internal HDLC controller may be attached to the

data link.

External Data Link

In T1 mode MT9074 has two pairs of pins (TxDL and

TxDLCLK,

RxDL

and

RxDLCLK)

dedicated

transmitting and receiving bits in the selected

overhead bit positions. Pins TxDLCLK and RxDLCLK

are clock outputs available for clocking data into the

MT9074 (for transmit) or external device (for receive

information). Each clock operates at 4 Khz. In the

SLC-96 mode the optional serial data link is

multiplexed into the Fs bit position. In the ESF mode

the serial data link is multiplexed into odd frames, i.e.

the FDL bit positions.

Bit - Oriented Messaging

In T1 mode MT9074 Bit oriented messaging may be

selected by setting bit 6 (BIOMEn) in the Data Link

Control Word (page 1H, address 12H). The transmit

data link will contain the repeating serial data stream

111111110xxxxxx0

where

the

byte

0xxxxxx0

originates

from

the

user

programmed

"Transmit Bit Oriented Message" - page 1H address

13H.

The

receive

BIOM

"Receive

Bit

Oriented Message" - page 3H, address 15H, will

contain

the

last

received

valid

message

(the

0xxxxxx0 portion of the incoming serial bit stream).

To prevent spurious inputs from creating false

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