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CHAPTER 5 SAR FUNCTION
145
Caution When packet transmission is stopped by a Deactivate_Channel command issued by the
host, make sure that the VC is inactive (the A bit of the VC table is 0) before issuing a
Tx_Ready command to the VC.
(5) Closing a transmit channel
To terminate the use of a channel, the host issues a Close_Channel command when the channel is in the
idle state. The channel can be placed in the idle state by emptying the transmit queue or by issuing a
Deactivate_Channel command.
When the host issues a Close_Channel command, the response returned is a Close_Channel indication. If
the indication has the VC NUMBER of a channel to be closed, it means that the Close_Channel command
was executed successfully. The
μ
PD98405 returns the VC table to the free block pool. Consequently, the
channel cease to exist and therefore enters the non-existent state.
If the host issues a Close_Channel command to a channel while it is in the idle state (A bit is "0"), a
Close_Channel indication, indicating a failure in closing the channel, may be returned as a response. This
is because the channel is in the idle state, but those cells in the internal transmit FIFO have not yet been
transmitted to the PHY layer. In this case, the
μ
PD98405 is performing internal processing related to the
channel and does not allow the VC table to be released. If the host receives a close failure indication, it
must continue to issue Close_Channel commands until one is accepted. If execution of a Close_Channel
command fails, the CD bit of the relevant VC table is set to 1.