ATM Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
39-15
39.4
Port-to-Port (PTP) Switching
The port-to-port (PTP) switching mechanism allows an ATM cell of any AAL type to be switched from
one ATM port to any other ATM port using the AAL0 format (no adaptation). This automatic PTP
switching requires no host intervention and can be dynamically activated per VC.
The advantages of ATM PTP switching include the following:
•
No host support needed for receive-side to transmit-side delivery.
•
Host performs only initialization and error handling (receiver busy exception).
•
Supports half- and full-duplex connections.
•
Can be activated per VC as programmed in the RCT. (Host-controlled switching can still be used
while PTP switching other channels.)
•
PPD support for switched connections with AAL5 content.
•
Can terminate OAM or management cells while PTP switching the data cells.
39.4.1
PTP Switching Mechanism
In the host-controlled method of ATM-to-ATM cell switching, the host application software handles the
BDs and transfers the buffer pointers from the RxBD table to the TxBD table.
Figure 39-9
shows the
host-controlled method with the option of using APC scheduling or using the apc bypass command.
Figure 39-9. Host-controlled Switching Serial ATM to a UTOPIA Channel
In contrast, the PTP switching mechanism does cell switching automatically. The cell is received directly
into the buffers of a common PTP BD table shared by the receive channel and the transmit channel
associated with the PTP connection.
Figure 39-10
shows the PTP switching method with an example of
switching a serial ATM channel to a UTOPIA channel.
Scc
UTOPIA
RxBD Table
TxBD Table
Host
Mem
Rx
Tx
Activated
channel?
APC
Bypass
TxBD Table
N
Y
PHY
Tx Queue
APC
Scheduling
Table
MPC885
Содержание PowerQUICC MPC870
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Страница 1068: ...ATM Pace Control MPC885 PowerQUICC Family Reference Manual Rev 2 40 22 Freescale Semiconductor ...
Страница 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
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Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
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