![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT94L33IB-L_datasheet_100163/XRT94L33IB-L_182.png)
XRT94L33
xr
Rev.1.2.0.
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
182
Bit 1 – Discard Cell Enable
This bit-field permits the user to configures the “Transmit User Cell” filter (within the Transmit ATM Cell
Processor block) either discard or not discard a given cell that complies with the “user-defined” filtering
requirements. Cells that are discarded will not be routed to the “Transmit STS-3c POH Processor” block.
Cells that are NOT discarded will proceed on through the remainder of the Transmit ATM Cell Processor
block circuitry, for further processing.
Setting this bit-field to “1” configures the Transmit User Cell Filter to discard all cells that comply with the
“user-cell” filter requirements.
Conversely, setting this bit-field to “0” configures the Transmit User Cell Filter to NOT discard the cells that
comply with the “user-cell” filter requirements.
2.2.6.3
DEFINING THE USER CELL FILTER SENSE
The Sense of a given Transmit User Cell Filter is defined by the state of Bit 0 (User Cell Filter Sense) within
the “Transmit ATM Filter Control – Byte 0” Register; as described below.
Bit 0 - User Cell Filter Sense
Transmit ATM Filter # 0 , # 1, # 2, # 3 Control – Byte 0 (Address = 0xNF43, 0xNF53, 0xNF63, 0xNF73)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
User Cell
Filter Enable
Copy Cell
Enable
Discard
Cell
Enable
User Cell
Filter Sense
R/O
R/W
0
1
X
This bit-field controls the “Filter Mode”. If the user sets this bit-field to “1” then the “Transmit User-Cell” Filter
will act, per the settings within Bits 2 (Copy Cell Enable) and 1 (Discard Cell Enable) on cells with header byte
patterns MATCHING the “user-cell” filtering criteria. Conversely, setting this bit-field to “0” configures the
“Transmit User-Cell” Filter to act, per the settings within Bits 2 (Copy Cell Enable) and 1 (Discard Cell Enable)
on cells with header byte patterns NOT MATCHING the “user-cell” filtering criteria.
2.2.6.4
SPECIFYING THE TRANSMIT USER CELL FILTERING CRITERIA
As described above, each of the four Transmit User Cell Filters (within the Transmit ATM Cell Processor
block) can be configured to perform a variety of actions (e.g., copy cells, discard cells, etc); based upon
whether the Header Byte Patterns of User Cells MATCH; or DO NOT MATCH a particular “User-Defined”
Filter criteria.
The “User-Defined” Filter criteria (for each of the four Transmit User Cell Filter blocks, within the Transmit
ATM Cell Processor block) are ultimately defined by the values residing within a total of eight (8) registers.
Four of these registers are referred to as “User Cell Filter – Pattern” Registers; and the remaining four
registers are referred to as “User Cell Filter – Check” Registers. Each of these register types are defined
below.