CN8223
1.0 Product Description
ATM Transmitter/Receiver with UTOPIA Interface
1.4 ATM Cell Processing Functions
1.4.1 Cell Generation Functions
The CN8223 ATM cell processing block provides flexible control for cell
generation. Cell generation is the formatting of 48-octet payload segments into
53-octet ATM cells, and the generation of appropriate header octets, HEC, and
payload Cyclic Redundancy Check (CRC) calculations as required by the AAL
formats. The CN8223 provides modes that perform this cell generation function,
along with modes that allow insertion of any or all of the various header fields
from either the FIFO interface or from microprocessor control registers. Four cell
generation modes are available in the CN8223. Cell generation functions are
described in detail in Section 2.6.
1.4.2 Tx Rate Control
Two Rate Control registers [0x08, 0x09] are provided for each of the four ports to
allow programmable rate shaping of cell transmission. The ratio of active to idle
cells is programmable with 0.4 % granularity. Status counts of non-idle cells
transmitted are maintained for each of the four sources.
1.4.3 Cell Validation Functions
Cell validation refers to the checking of cells coming in from the PHY block for
proper format. The CN8223 provides modes that deliver 48-, 52-, or 53-octet
cells, or 57-octet PLCP slots to the FIFO output ports. The validation process is
described in detail in Section 2.6.
Protocol verification includes HEC validation with ATM or SMDS/802.6
coverage, validation of payload length per segment type, and correct payload
CRC value. Status reporting of validation steps is via error counters and status
register indications. Status bits can be programmed to generate interrupts to the
microprocessor. Each validation step can be individually disabled.
100046C
Conexant
1-9
CONEXANT [ CONEXANT SYSTEMS, INC ]
