EB632 datasheet(46/112 Pages) FREESCALE

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Functional Differences Between MSC8101 (Mask 2K42A) and MSC8103 (Mask 2K87M), Rev. 2

Freescale Semiconductor

CPM

The RCF can perform single bit error correction on the header. If multiple bit errors are found in the HEC, the cell

is discarded. If the single bit error correction mode is not enabled (TCMODE[SBC] = 1), the cell is also discarded

when a single bit error is found in the header.

When the cell delineation state machine is in the SYNCH state, the HEC verification state machine (see Figure 17)

implements the correction algorithm. This state machine ensures that a single cell header is corrected at a time. If

consecutive cells are detected with single bit errors in their headers, only the first cell error is corrected and the rest

are discarded. This state machine reduces the delivery of cells with headers containing errors under bursty error

conditions.

The RCF can also perform idle/unassigned cell filtering. Both features are programmable (TCMODE[CF]). Cells

that are detected to be idle/unassigned are discarded, that is, not forwarded to the UTOPIA interface Rx FIFO.

14.4.6 Receive ATM 2-Cell FIFO

The receive FIFO provides FIFO management and an interface to the UTOPIA receive cell interface. The receive

FIFO can hold 2 ATM cells, thereby providing the cell rate decoupling function between the transmission system

physical layer and the ATM layer. FIFO management includes filling the FIFO, indicating to the UTOPIA interface

that it contains cells, maintaining the FIFO read and write pointers, and detecting FIFO overrun (TCER[OR])

conditions.

14.4.7 Transmit ATM Cell Functions

The transmit ATM cell functions block (TCF) performs the ATM cell payload scrambling and is responsible for the

HEC generation and the idle/unassigned cell generation. The TCF scrambles (programmable by the user) the cell

payload using the self-synchronizing scrambler with polynomial x

43 + 1. The HEC is generated using the

polynomial x8 + x2 + x + 1. The coset polynomial x6 +x4 + x2 + 1 is added (modulo 2) (programmable by the user)

to the calculated HEC octet. The result overwrites the HEC octet on the transmitted cell. When the transmit FIFO is

empty, the TCF inserts idle/unassigned cells (counted in ICC). The TCF accumulates the number of transmitted

assigned cells in a counter (TCC).

14.4.8 Transmit ATM 2-Cell FIFO

The transmit FIFO provides FIFO management and an interface to the UTOPIA transmit interface. The FIFO

provides the cell rate decoupling between the transmission system physical layer and the ATM layer.

Figure 17. HEC: Receiver Modes of Operation

Detection

Correction

Multi-bit error

Mode

detected

(Cell discarded)

No error detected

(correction)

Single-bit error detected

Error detected

(Cell discarded)

No error detected

(No action)

EB632 Datasheet(PDF) 46 Page - Freescale Semiconductor, Inc

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