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PM7348 参数 Datasheet PDF下载

PM7348图片预览
型号: PM7348
PDF下载: 下载PDF文件 查看货源
内容描述: [ATM/SONET/SDH IC, CMOS, PBGA324,]
分类和应用: ATM异步传输模式
文件页数/大小: 318 页 / 1736 K
品牌: PMC [ PMC-SIERRA, INC ]
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S/UNI-IMA-4 Telecom Standard Product Data Sheet  
Released  
Similarly, the first stuff cell insertion on the previous TRL occurs in approximately the same  
frame a stuff cell would have been inserted had it still been the TRL although the actual frame  
for stuff insertion will also be dependent on the rate difference with the new TRL. This  
minimizes any effects on the differential delay for the group as well as reducing any FIFO level  
changes. All subsequent stuff cell insertions on the TRL then happen after every 2048 cells and  
all subsequent stuff cell insertions on the former TRL are dependent only on the link’s rate  
difference from the new TRL.  
10.2.4 Receive IMA Data Processor (RDAT)  
The Receive IMA Data Processor (RDAT) performs the IMA data-flow functions in the receive  
direction including the IMA Frame Synchronization Mechanism (IFSM), storage of data for  
accommodating differential delay, defect detection, and playout of data in a round robin fashion.  
One 16 Mbit (1 Mbit x 16) SDRAM, available as a single chip device, is required. Differential-  
delay tolerance may be configured through registers on a per-group basis to any value up to the  
maximum listed in Figure 11. Buffering is allocated on a per link basis. Each link is allocated  
the same number of cell buffers. Each link is allocated 1024 cell buffers. See Figure 11 for the  
required memory sizes.  
Figure 11 Max Differential Delay Tolerance  
# of T1/E1  
Links  
4 T1/ 4 E1  
Cells of  
B uffering in m s  
1024 282 m s  
Delay (T1) Delay (E 1) in S DRAM  
m s  
size  
226 m s 1M bit x16  
Writing data to the Delay Compensation Buffers (DCB)  
When there is a full cell of data in the RX Link FIFOs, the link requests service. The RDAT  
arbitrates between links requiring service in a round-robin fashion.  
When a link is chosen for service, if it is not an IMA link, the cells are stored in external  
memory in a per link FIFO.  
For IMA links, the IFSM is performed to locate the IMA Frame. Once the IMA frame is located,  
the RDAT calculates the location to store the cells. The cells are stored in a time-based FIFO  
structure. The buffer address for a cell is created from the cell number in the IMA frame  
concatenated with the lower x (depends upon M) bits of the IMA frame sequence number. Each  
link has its own reserved FIFO. The cells are stored in this manner such that they are aligned in  
time in the external memory and the differential-delay removal is simplified.  
During periods in which the link is in a defect state, incoming cells will be replaced with filler  
cells prior to being written to the DCB.  
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.  
Document No.: PMC-2020889, Issue 2  
57