MT9079AC datasheet(18/54 Pages) MITEL

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MT9079

4-254

Circular Buffers

The MT9079 is equipped with two 16 byte circular

receive buffers and two 16 byte circular transmit

buffers, which can be connected to any PCM 30 time

slot. Connection is made through control bits 3 to 0

of the per time slot control words on pages 7 and 8.

These buffers will transmit and receive time slot data

synchronously with the CRC-4 multiframe.

Transmit circular buffer zero is located on page 9

(TxB0.0 to TxB0.15) and transmit circular buffer one

is located on page 10 (TxB1.0 to TxB1.15).

The two circular 16 byte receive buffers (page 11 -

RxB0.0 to RxB0.15 and page 12 - RxB1.0 to

RxB1.15) record the data received in an associated

channel for the next 16 frames beginning with the

CRC-4 multiframe boundary. The assigned channel

data from the next multiframe will over-write the

current data until the buffer is disconnected.

The STOP and START maskable interrupts extend

the normal operation of the receive buffers in the

following manner.

a) STOP - once activated, receive circular buffer 0 or

1 records time-slot data until that data either

matches or mismatches a user-defined eight bit

pattern, then the interrupt occurs. This user-defined

bit pattern is determined by the Code Detect Word

(CDW) and Detect Word Mask (CDM) mentioned

below.

b) START - once activated, receive circular buffer 0

or 1 begins recording time-slot data and initiates an

interrupt when a user-defined eight bit pattern is

received. This user-defined bit pattern is determined

by the Code Detect Word (CDW) and Detect Word

Mask (CDM) mentioned below.

The functionality and control of the START and

STOP interrupts is described in Table 6.

PCM 30 Time-Slot Code Insertion and Detection

Idle line codes, flags or user-defined codes can be

inserted and detected on any combination of PCM 30

time-slots. This is done as follows:

a) CIW7-0 - Code Insert Word 7 to 0 (page 1, address

17H) is an eight bit code that is transmitted on

user-defined PCM 30 time-slots. Transmit time-slots

are selected through bit 7 of the per time slot control

words (pages 7 and 8).

b) CDW7-0 - Code Detect Word 7 to 0 (page 1,

address 18H) is an eight bit code, which is compared

with the contents of user-defined PCM 30 receive

time-slots. When the contents of the selected channels

matches the CDW7-0 the DATA interrupt, if unmasked,

will be triggered. Receive time-slots are selected

Notes:

1) The interrupt vector value associated with these interrupts is 02H (page 4, address 12H)

The START and STOP interrupts can be used to record the data between two pre-defined eight bit data patterns received in a

particular pattern.

3) Circular Buffer Accumulate Control Word (page 2, address 12H).

Interrupt

Mask

Function*

(note 3)

Description (see notes 1 and 2)

STOP

(page 1,

address

1EH, bit 2)

STOP0

Circular buffer zero stops recording on a match with CDW and CDM.

STOP1

Circular buffer one stops recording on a match with CDW and CDM.

STOP0

Circular buffer zero stops recording on a mismatch with CDW and

CDM.

STOP1

Circular buffer one stops recording on a mismatch with CDW and

CDM.

START

(page 1,

address

1EH, bit 1)

START0

Circular buffer zero starts recording on a match with CDW and CDM.

START1

Circular buffer one starts recording on a match with CDW and CDM.

START0

Circular buffer zero starts recording on a mismatch with CDW and

CDM.

START1

Circular buffer one starts recording on a mismatch with CDW and

CDM.

Table 6 - START and STOP Interrupt Control

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