![](http://datasheet.mmic.net.cn/380000/-PD98405_datasheet_16745025/-PD98405_144.png)
CHAPTER 5 SAR FUNCTION
144
Figure 5-18. Status Transition of Transmit Channel
Non-existent status
Close_Channel command
Open_Channel command
Tx_Ready command
Empty transmit queue or
Deactivate_Channel command
Idle status
Active status
(4) Transmit Deactivate_Channel command
The
μ
PD98405 can forcibly stop the use of a channel for transmission and return it to the idle state, using
the Deactivate_Channel command. When the host issues a Deactivate_Channel command during packet
transmission, the
μ
PD98405 stops packet transmission and prepares a final user abort cell. The final user
abort cell is a final AAL-5 PDU cell in which the AAL-5 trailer packet length field (Length) is "0." The final
user abort cell is shown below.
Figure 5-19. Final User Abort Cell
53 bytes
CPI
"all 0"
CRC-32
Padding
"all 0"
Header
Trailer
Length
"all 0"
5 bytes
2 bytes
4 bytes
1 byte
1 byte
40 bytes
C
"
Usually, if the receiving end receives a final user abort cell, it discards the relevant packet.
Upon receiving a Deactivate_Channel command during packet transmission, the
μ
PD98405 terminates
packet transmission immediately, then transmits all the cells in its internal transmit FIFO and a final user
abort cell, in that order. Next, it issues an interrupt to the host in the same manner as at the normal end of
packet transmission, and stores the relevant indication into the mailbox. The A bit of this indication is set to
"0."
The indication is also issued even when the Deactivate_Channel command is received during the
transmission of a packet with its indication masked (with the IM bit of the packet descriptor set to 1).
If the
μ
PD98405 receives a Deactivate_Channel command when a packet is not being transmitted, the
μ
PD98405 ignores the command and does not transmit a final user abort cell.
When packet transmission is stopped by the Deactivate_Channel command, the address of the next
packet to the stopped packet is stored in Tx QUEUE READ POINTER of the transmit VC table.