MT9079AC datasheet(17/54 Pages) MITEL

17 / 54 page

MT9079

4-253

CRC Error and E-bit Counters

CRC-4 errors and E-bit errors are counted by the

MT9079 in order to support compliance with CCITT

requirements. These eight bit counters are located

on page 4, addresses 1FH and 1EH respectively.

They are incremented by single error events, which

is a maximum rate of twice per CRC-4 multiframe.

There are two maskable interrupts associated with

the CRC error and E-bit error measurement. CRCI

and EBI are initiated when the least significant bit of

the appropriate counter toggles, and CRCO and

EBO are initiated when the appropriate counter

changes from FFH to 00H.

G.821 Bit Error Rate Estimation

A G.821 BERT estimation for an E1 link can be done

with either the BERT counter, when it is associated

with the FAS, or the Errored Frame Alignment Signal

counter. It should be noted that the BERT counter

will be incremented once for every bit error found in

the FAS, and not just once for every FAS in error.

The formula for the link BERT estimation is as

follows:

BERT estimation = BERT counter value/(N*F*T)

where:

N is the number of bits verified (i.e., when the FAS

is used N = 7; when a channel is selected N = 8).

F is the number of FAS or channels in one second

(i.e., when the FAS is used F= 4000, when a

channel is selected F = 8000).

T is the elapsed time in seconds.

A similar formula can be used with the FAS error

counter.

BERT estimation = FAS Error counter value/(7*4000*T).

The CRC-4 error counter can also be used for BERT

estimation. The formula for BERT estimation using

the CRC-4 error count is as follows:

BERT estimation = CEt counter value/(2048000*T)

where:

2048000 is the number of bits that are

received in one second.

T is the elapsed time in seconds.

A similar formula can be used to provide a BERT

estimation of the transmit direction by using the E-bit

error counter, EBt.

A more accurate BERT estimation can be done using

the Bipolar Violation Error counter. The BPV error

counter will count violations that are not due to HDB3

encoding. The formula for this is as follows:

BERT estimation = BPV Error counter value/(256*8000*T)

where:

256 is the number of bits per basic frame.

8000 is the number of basic frames in one second.

T is the elapsed time in seconds.

This assumes that one BPV error will be the result of

one bit error.

RAI and Continuous CRC-4 Error Counter

When the receive Remote Alarm Indication is active

(RAI = 1 - bit 3 of the NFAS) and a receive E-bit

indicates a remote error (En = 0), the RCRC counter

will be incremented. This counter will count the

number of submultiframes that were received in error

at the remote end of a link during a time when layer

one capabilities were lost at that end. This eight bit

RCRC counter is located on page 4, addresses 19H.

There are two maskable interrupts associated with

the RCRC counter. RCRI is initiated when the least

significant bit of the RCRC counter toggles, and

RCRO and EBO are initiated when the counter

changes from FFH to 00H.

Maintenance and Alarms

Error Insertion

Five types of error conditions can be inserted into the

transmit PCM 30 data stream through control bits,

which are located on page 2, address 10H. These

error events include the bipolar violation errors

(BPVE), CRC-4 errors (CRCE), FAS errors (FASE),

NFAS errors (NFSE), and a loss of signal condition

(LOSE). The LOSE function overrides the HDB3

encoding function.

MT9079AC Datasheet(PDF) 17 Page - Mitel Networks Corporation

MT9079AC Datasheet(HTML) 17 Page - Mitel Networks Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Datasheet Download

Link URL