zl50118gag2 Zarlink Semiconductor, zl50118gag2 Datasheet - Page 54

• Manufacturer Part Number: zl50118gag2
• Description: 32 Channel 1 T1/e1 Cesop Processor With Single Ethernet Interface
• Manufacturer: Zarlink Semiconductor

In applications where large payloads are being used, the payload size must be chosen such that the overall packet
size does not exceed the maximum Ethernet packet size of 1518 bytes (1522 bytes with VLAN tags). Figure 17
shows the packet format for structured TDM data, where the payload is split into frames, and each frame
concatenated to form the packet.
6.5.1.1
Packets are assembled sequentially, with each channel placed into the packet as it arrives at the TDM
Interface. A fixed order of channels is maintained (see Figure 18), with channel 0 placed before channel 1,
which is placed before channel 2. It is this order that allows the packet to be correctly disassembled at the far
end. A context must contain only unique channel numbers. As such a context that contains the same channel
from different streams, for example channel 1 from stream 2 and channel 1 from stream 3, would not be
permitted.
Each packet contains one or more frames of TDM data, in sequential order. This groups the selected channels
for the first frame, followed by the same set of channels for the subsequent frame, and so on.
6.5.2
In unstructured mode, the payload is not split by defined frames or timeslots, so the packet consists of a continuous
stream of data. Each packet consists of a number of octets, as shown in Figure 19. The number of octets in a
packet need not be an integer number of frames. A typical value for N may be 192, as defined in the IETF PWE3
RFC.
For example, consider mapping the unstructured data of a 25 timeslot DS0 stream. The data for each T1 frame
would normally consist of 193 bits, 192 data bits and 1 framing bit. If the payload consists of 24 octets it will be 1 bit
short of a complete frames worth of data, if the payload consists of 25 octets it will be 7 bits over a complete frames
worth of data. NOTE: No alignment of the octets with the T1 framing structure can be assumed.
Unstructured Payload Operation
Payload Order
S tre a m 0
S tre a m 1
S tre a m 2
S tre a m 3
C h a n n e l 0
C h a n n e l 0
C h a n n e l 0
C h a n n e l 0
Figure 18 - Channel Order for Packet Formation
ZL50115/16/17/18/19/20
C h a n n e l 1
C h a n n e l 1
C h a n n e l 1
C h a n n e l 1
Zarlink Semiconductor Inc.
C h a n n e l 2
C h a n n e l 2
C h a n n e l 2
C h a n n e l 2
C h a n n e l A s se m b ly O rd e r
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C h a n n e l 3 1
C h a n n e l 3 1
C h a n n e l 3 1
C h a n n e l 3 1
Data Sheet