ZL50119 Datasheet, PDF (52/95 Pages) Zarlink Semiconductor Inc – 32, 64 and 128 Channel CESoP Processors

ZL50115/16/17/18/19/20
Data Sheet
6.4.1 Structured Payload Operation
In structured mode a context may contain any number of 64 kbps channels. These channels need not be
contiguous and they may be selected from any input stream.
Channels may be added or deleted dynamically from a context. This feature can be used to optimize bandwidth
utilisation. Modifications to the context are synchronised with the start of a new packet.
The fixed header at the start of each packet is added by the Packet Transmit block. This consists of up to 64 bytes,
containing the Ethernet header, any upper layer protocol headers, and the two byte context descriptor field (see
section below). The header is entirely user programmable, enabling the use of any protocol.
The payload header and size must be chosen so that the overall packet size is not less than 64 bytes, the Ethernet
standard minimum packet size. Where this is likely to be the case, the header or data must be padded (as shown in
Figure 17 and Figure 19) to ensure the packet is large enough. This padding is added by the ZL5011x for most
applications.
Header
Data for TDM Frame 1
Data for TDM Frame 2
Ethernet Header
Network Layers
(added by Packet Transmit)
Upper layers
(added by Protocol Engine)
Channel 1
Channel 2
Channel x
Channel 1
Channel 2
Channel x
may include VLAN tagging
e.g. IPv4, IPv6, MPLS
e.g. UDP, L2TP, RTP,
CESoPSN, SAToP
TDM Payload
(constructed by Payload Assembler)
Data for TDM Frame n
Channel 1
Channel 2
Channel x
Static Padding
(if required to meet minimum payload size)
Ethernet FCS
may also be placed in the
packet header
Figure 17 - ZL50115/16/17/18/19/20 Packet Format - Structured Mode
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.
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