MH89770 datasheet(16/36 Pages) MITEL

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MH89770

Preliminary Information

Figure 8 - Off-Line Framer State Diagram

Hunt Mode

False Candidate

False

Candidate

Forced

Reframe

Out of

Sync.

False

Candidate

Verify

Candidate

CRC

Check

In sync

Candidate

Valid Candidate

Maintenance

Resync

Receiver

Valid Candidate

New Frame Position

* Note: Only when in ESF mode and CRC

option is enabled.

Setting CRC/MIMIC bit high will force the framer to

synchronize to the first terminal framing pattern

detected. In standard D3/D4 applications, the user’s

system software should monitor the multiframe

synchronization state indicated by bit 3 in Master

Status Word 1. Failure of the device to achieve

multiframe synchronization within 4.5ms of terminal

frame synchronization, is an indication that the

device has framed up to a terminal framing pattern

mimic and should be forced to reframe.

One of the main features of the framer is that it

performs its function “off line”. That is, the framer

repositions the receive circuit only when it has

detected a valid frame position. When the framer

exits maintenance mode the receive counters remain

where they are until the framer has found a new

frame position. This means that if the user forces a

reframe when the device was really in the right

place, there will not be any disturbance in the circuit

because the framer has no effect on the receiver

until it has found synchronization.

The out of

synchronization criterion can be controlled by bit 0 in

Master Control Word 2. This bit changes the out of

frame conditions for the maintenance state.

MH89770 Datasheet(PDF) 16 Page - Mitel Networks Corporation

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