cx28224 Mindspeed Technologies, cx28224 Datasheet - Page 88

• Manufacturer Part Number: cx28224
• Description: Cx28224/5/9 Inverse Multiplexing For The Atm Ima Family
• Manufacturer: Mindspeed Technologies

Transmission Convergence Block
5.2.3
5-6
Cell Screening
The CX2822x provides two optional types of cell screening. The first type, idle cell
rejection, prevents idle cells from being passed on. The second type, user traffic
screening, compares incoming bits to the values in the receive cell header registers.
Cells are rejected or accepted based on the bit patterns of their headers.
Idle cell rejection is enabled in bit 6 of the CVAL register (0x0C). If this bit is set to 1,
all incoming cells that match the contents of the Receive Idle Cell Header Control
Registers, RXIDL1–4 (0x20–23), are rejected. Individual bits in the Receive Idle Cell
Mask Control Registers, IDLMSK1–4 (0x24–27), can be set to 1 or Don’t Care,
causing the corresponding bits of the incoming cell to be treated as matching,
regardless of their value. If idle cell rejection is disabled, cells pass directly to user
traffic screening.
User traffic cell screening is similar to idle cell screening in that the incoming cells
are compared to the Receive Cell Header Control Registers, RXHDR1–4 (0x18–1B).
Individual bits in the Receive Cell Mask Control Registers, RXMSK1–4 (0x1C–1F),
can be set to 1 or Don’t Care, causing the corresponding bits of the incoming cell to be
treated as matching, regardless of their values. The RejHdr bit (bit 7) in the CVAL
register (0x0C) determines whether matching cells are rejected or accepted. If it is set
to 0, matching cells are accepted. If it is set to 1, matching cells are rejected. See
Table 5-2
Table 5-2. Cell Screening—Matching
Table 5-3. Cell Screening—Accept/Reject Cell
Receive Cell Mask Bit
Match
Match
Cell
and
Fail
Fail
0
0
0
0
1
Mindspeed Technologies
Table
5-3.
Receive Cell Header Bit
Reject Header
0
0
1
1
x
0
1
0
1
™
Accept Cell
Reject Cell
Reject Cell
Accept Cell
Incoming Bit
Result
0
1
0
1
x
Match
Fail
Fail
Match
Match
CX28224/5/9 Data Sheet
28229-DSH-001-D
Result