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PM7346 S/UNI-QJET
DATASHEET
PMC-960835
ISSUE 6
SATURN QUAD USER NETWORK INTERFACE FOR J2, E3, T3
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND ITS CUSTOMERS’ INTERNAL USE
220
Table 17
- RXCP-50 Cell Delination Algorithm Base
ALIGN[1:0]
Cell Delineation Algorithm base
00
Bit
01
Nibble (DS3)
10
Byte (E3,J2, E1, T1)
11
Unused
IN52:
The IN52 bit defines the number of bytes contained in incoming cells. When
IN52 is a logic '0', incoming cells are 53 bytes in length. When IN52 is a logic
'1', incoming cells are 52 bytes in length. In order for ATM cell delineation to
function properly, incoming cells must be 53 bytes in length including a valid
HCS byte. The HCS byte can be stripped off on the Utopia side using the
DS27_53 register bit. If the S/UNI QJET is operating in PPP mode, incoming
"cells" may be composed of 52 or 53 bytes without an HCS byte. In this case,
the CCDIS register bit should be set to disable cell delineation, and the
DS27_53 register bit should be set so that it is consistent with IN52.
IDLEPASS:
The IDLEPASS bit controls the function of the Idle Cell filter. When
IDLEPASS is written with a logic 0, all cells that match the Idle Cell Header
Pattern and Idle Cell Header Mask are filtered out. When IDLEPASS is a
logic 1, the Idle Cell Header Pattern and Mask registers are ignored. The
default state of this bit and the bits in the Idle Cell Header Mask and Idle Cell
Header Pattern Registers enable the dropping of idle cells.
HCSPASS:
The HCSPASS bit controls the dropping of cells based on the detection of an
uncorrectable HCS error. When HCSPASS is a logic 0, cells containing an
uncorrectable HCS error are dropped. When HCSPASS is a logic 1, cells are
passed to the receive FIFO regardless of errors detected in the HCS.
Additionally, the HCS verification finite state machine never exits the
correction mode.
Regardless of the programming of this bit, cells are always dropped while the
cell delineation state machine is in the 'HUNT' or 'PRESYNC' states unless
the CCDIS bit in this register is set to logic 1.