MT90883 Zarlink Semiconductor, MT90883 Datasheet - Page 38

• Manufacturer Part Number: MT90883
• Description: (MT90880 - MT90883) TDM to Packet Processors
• Manufacturer: Zarlink Semiconductor

5.5.3
Context modification must be an atomic operation. Therefore, if the host modifies the context setup, it must wait
until that change has been carried out before attempting further modifications. This will take a bounded but
indeterminate time, since the context will not actually be modified until the start of the next new packet. The
context state machine will set a flag to indicate to the host that it is in the process of modifying the context, and
that the host should refrain from further updates.
However, distinct contexts can be modified simultaneously, since each context is completely independent from
any other. As a consequence, the MT9088x family supports a cross-connect service, where each context (or
virtual channel) can be sent over the packet network to a different terminating device. The context modification
process is shown in Table 4.
1
2
3
4
5
6
7
PTX Host modifies an existing context to add or
delete channels.
PTX Host signals Packet Receive host to expect a
modified context, with details of the channels to be
added or deleted, and their destination channels.
PTX host activates the previously programmed
context change.
At the start of the next new packet, the MT9088x
commences formation of the first packet for the
modified context. This packet is prepended with the
new packet header, with the context switch bit
toggled.
Context Modification (Addition or deletion of physical channels)
Packet Transmit End (PTX)
Table 16 - Context Modification Process
Zarlink Semiconductor Inc.
MT90880/1/2/3
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PRX Host modifies receive context concerned.
PRX host sends an acknowledgement back to the
PTX that the context has been modified and is
ready to receive packets.
First packet received for the modified context,
identified by the toggling of the context switch bit.
This automatically activates the previously
programmed context modifications. The new value
of the context switch bit is recorded for reference.
Packet Receive End (PRX)
Data Sheet