MT9072AB datasheet(43/275 Pages) ZARLINK

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MT9072

Data Sheet

Zarlink Semiconductor Inc.

4.0

PCM30 Interface (E1)

4.1

E1 Interface to the System Backplane

PCM30 (E1) basic frames are 256 bits long and are transmitted at a frame repetition rate of 8000 Hz, which results

in an aggregate bit rate of 256 bits x 8000/sec = 2.048 Mbits/sec. The actual bit rate is 2.048 Mbit/s +/-50 ppm

encoded in HDB3 (High Density Bipolar 3) format. Basic frames are divided into 32 timeslots numbered 0 to 31, see

Figure 6. Each timeslot is 8 bits in length and is transmitted most significant bit first (numbered bit 1). This results in

a single timeslot data rate of 8 bits x 8000/sec. = 64 kbit/s.

It should be noted that the Zarlink ST-BUS also has 32 channels numbered 0 to 31, but the most significant bit of an

eight bit channel is numbered bit 7, see Figure 5. Therefore, ST-BUS bit 7 is synonymous with PCM30 bit 1; bit 6

with bit 2: and so on, see Zarlink Application Note MSAN-126 for more details on the ST-BUS.

Tables 4 and 5 show the mapping between the ST-BUS channels and the PCM30 timeslots.

When the device is in IMA (Inverse Mux for ATM) mode the mapping between the ST-BUS Channels and the

PCM30 timeslots is according to Table 4.

PCM30 timeslot 0 is reserved for basic frame alignment, CRC-4 multiframe alignment and the communication of

maintenance information (facility data link). In most configurations timeslot 16 is reserved for either Channel

Associated Signaling (CAS or ABCD bit signaling) or Common Channel Signaling (CCS). For V5.2 applications,

timeslots 15, 16 and 31 may be used for CCS. The remaining timeslots are called channels and carry either PCM

encoded voice signals or digital data. Channel alignment and bit numbering is consistent with timeslot alignment

and bit numbering. However, channels are numbered 1 to 30 and relate to timeslots as per Table 6.

PCM30 Timeslots

56789

ST-BUS Channels

(DSTi/o and CSTi/o)

56789

PCM30 Timeslots

24252627282930

ST-BUS Channels

(DSTi/o and CSTi/o)

Table 4 - ST-BUS Channel vs. PCM30 Timeslot for 2.048 Mbit/s DST/CST Streams (E1)

PCM30 Timeslots

234

101112

ST-BUS

F0/4

Chan(DSTi/o F1/5

and CSTi/o) F2/6

F3/7

PCM30 Timeslots

1617181920

2223

ST-BUS

F0/4

Chan(DSTi/o F1/5

and CSTi/o) F2/6

F3/7

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

Table 5 - ST-BUS Channel vs. PCM30 Timeslot Relationship for 8.192 Mbit/s DST/CST Streams (E1)

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