MT9075BP1 Zarlink, MT9075BP1 Datasheet - Page 27

• Manufacturer Part Number: MT9075BP1
• Description: PB FREE E1 SINGLE CHIP TRANSCEIVER
• Manufacturer: Zarlink

and the next FAS is correct, the algorithm declares that basic frame synchronization has been found (i.e., page
03H, address 10H, bit 7, SYNC is zero).
Once basic frame alignment is acquired the signalling and CRC-4 multiframe searches will be initiated. The
signalling multiframe algorithm will align to the first multiframe alignment signal pattern (MFAS = 0000) it receives in
the most significant nibble of channel 16 (page 3, address 10H, bit 6, MFSYNC = 0). Signalling multiframing will be
lost when two consecutive multiframes are received in error.
The CRC-4 multiframe alignment signal is a 001011 bit sequence that appears in PCM 30 bit position one of the
NFAS in frames 1, 3, 5, 7, 9 and 11 (see Table 7). In order to achieve CRC-4 synchronization two CRC-4 multiframe
alignment signals must be received without error (page 03H, address 10H, bit 5, CRCSYN = 0) within 8 msec.
The MT9075B framing algorithm supports automatic interworking of interfaces with and without CRC-4 processing
capabilities. That is, if an interface with CRC-4 capability, achieves valid basic frame alignment, but does not
achieve CRC-4 multiframe alignment by the end of a predefined period, the distant end is considered to be a non-
CRC-4 interface. When the distant end is a non-CRC-4 interface, the near end automatically suspends receive
CRC-4 functions, continues to transmit CRC-4 data to the distant end with its E-bits set to zero, and provides a
status indication. Naturally, if the distant end initially achieves CRC-4 synchronization, CRC-4 processing will be
carried out by both ends. This feature is selected when control bit AUTC (page 01H, address 11H) is set to zero.
Notes for Synchronization State Diagram (Figure 10)
1. The basic frame alignment, signalling multiframe alignment, and CRC-4 multiframe alignment functions operate
2. The receive channel associated signalling bits and signalling multiframe alignment bit will be frozen when multi-
3. Manual re-framing of the receive basic frame alignment and signalling multiframe alignment functions can be
4. The transmit RAI bit will be one until basic frame alignment is established, then it will be zero.
5. E-bits can be optionally set to zero until the equipment interworking relationship is established. When this has
6. All manual re-frames and new basic frame alignment searches start after the current frame alignment signal
7. After basic frame alignment has been achieved, loss of frame alignment will occur any time three consecutive
8. When CRC-4 multiframing has been achieved, the primary basic frame alignment and resulting multiframe
in parallel and are independent.
frame alignment is lost.
performed at any time.
been determined one of the following will take place:
a. CRC-to-non-CRC operation - E-bits = 0,
b. CRC-to-CRC operation - E-bits as per G.704 and I.431.
position.
incorrect basic frame alignment signals are received. Loss of basic frame alignment will reset the complete
framing algorithm.
alignment will be adjusted to the basic frame alignment determined during CRC-4 synchronization. Therefore,
the primary basic frame alignment will not be updated during the CRC-4 multiframing search, but will be updated
when the CRC-4 multiframing search is complete.
Zarlink Semiconductor Inc.
MT9075B
27
Data Sheet