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CMX608 参数 Datasheet PDF下载

CMX608图片预览
型号: CMX608
PDF下载: 下载PDF文件 查看货源
内容描述: [Integrated Input and Output Channel Filters]
分类和应用:
文件页数/大小: 70 页 / 3411 K
品牌: CMLMICRO [ CML MICROCIRCUITS ]
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RALCWI Vocoder  
CMX608/CMX618/CMX638  
5.5.2.  
Packets of FEC Protected Frames  
The device has a built-in FEC system to protect the Vocoder frames when transported over an error prone  
channel. The data interleaving has been organised to provide good performance over a channel with burst  
errors, typical in wireless applications. Only the bits that are more sensitive to corruption are protected  
FEC can be applied over 3 or 4 frames resulting in a packet of 216 or 288 bits, regardless of the Vocoder  
bit rate. The bits in the packet are named D0 through D215 (or D287). The bits should be transmitted in  
order, starting with D0 and ending with D215 (or D287).  
Hard-bits  
Hard bits are represented by one bit per bit. These are packed into 27 bytes for 3-frame FEC and 36 bytes  
for 4-frame FEC. The following table shows how these bits are packed and transferred between the  
Vocoder and the host microprocessor. The byte at the top is the first out of the C-BUS for the encoder and  
the first into the C-BUS for the decoder.  
7
6
5
4
3
2
1
0
D0  
D8  
D1  
D9  
D2  
D10  
D3  
D11  
D4  
D5  
D6  
D7  
D12  
D13  
D14  
D15  
Intervening bits follow the same pattern  
D200  
D208  
D201  
D209  
D202  
D210  
D203  
D211  
D204  
D212  
D205  
D213  
D206  
D214  
D207  
D215  
For 4 frame packets, the sequence continues thus...  
D272  
D280  
D273  
D281  
D274  
D282  
D275  
D283  
D276  
D284  
D277  
D285  
D278  
D286  
D279  
D287  
Soft-bits  
Soft bits are represented by one nibble per bit. These should be packed into 108 bytes for a 3-frame FEC  
and 144 bytes for a 4-frame FEC. The following table shows how these bits should be packed and sent to  
the decoder over the C-BUS. The byte at the top should be the first one sent. The bits of a nibble are  
shown as n3 to n0, with n3 being the most significant and n0 being the least significant.  
7
6
5
4
3
2
1
0
n3  
D0  
D2  
n2  
n1  
n0  
n3  
D1  
D3  
n2  
n1  
n0  
Intervening bits follow the same pattern  
D212  
D214  
D213  
D215  
For 4 frame packets, the sequence continues thus...  
D284  
D286  
D285  
D287  
2014 CML Microsystems Plc  
22  
D/608_18_38/11  
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