Motorola PowerQUICC II MPC8280 Series Reference Manual page 1023

current RxBD, sets RxBD[SNE], and returns to the hunt state. The receiver then waits for
a cell with a valid structured pointer to regain synchronization.
The MPC8280 supports partially filled cells configured on a per-VC basis. In this mode
(RCT[PFM] = 1), the ATM controller copies only the valid octets from the cell user data
field to the buffer.
31.2.2.2.1 AAL1 CES Receiver Overview
Refer to Section 32.3, "AAL1 CES Receiver Overview."
31.2.2.3 AAL0 Receiver Overview
For AAL0, no specific adaptation layer processing is done. The ATM controller copies the
whole cell to an external buffer. Each buffer contains exactly one AAL0 cell. The ATM
controller calculates and checks the CRC10 of the cell payload and sets RxBD[CRE] if a
CRC error occurs. AAL0 mode can be useful for receiving OAM cells or AAL3/4 raw cells.
31.2.2.4 AAL2 Receiver Overview
Refer to Section 33.4.1, "Receiver Overview."
31.2.3 Performance Monitoring
The ATM controller supports performance monitoring testing according to ITU I.610.
When performance monitoring is enabled, the ATM controller automatically generates and
terminates FMCs (forward monitoring cells) and BRCs (backward reporting cells). See
Section 31.6.6, "Performance Monitoring."
31.2.4 ABR Flow Control
When AAL5-ABR is enabled, the ATM controller implements the ATM Forum TM 4.0
available-bit-rate flow. It automatically inserts forward- and backward-RM cells into the
user cell stream and adjusts the transmission rate according to the backwards RM cell
feedback; see Section 31.10.2.2.2, "AAL5-ABR Protocol-Specific RCT." The ABR flow
is controlled on a per-VC basis.
31.3 ATM Pace Control (APC) Unit
The ATM pace control (APC) unit schedules the ATM channels for transmitting. While
performing this task, the APC unit uses the following parameters:
• Frequency (bandwidth) of each ATM channel
• ATM traffic pacing—Peak cell rate (PCR), sustain cell rate (SCR), and minimum
rate (MCR)
MOTOROLA Chapter 31. ATM Controller and AAL0, AAL1, and AAL5
Freescale Semiconductor, Inc.
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ATM Pace Control (APC) Unit
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