cx28250 Mindspeed Technologies, cx28250 Datasheet - Page 69

• Manufacturer Part Number: cx28250
• Description: Cx28250 Atm Physical Interface Phy Devices
• Manufacturer: Mindspeed Technologies

CX28250
ATM Physical Interface (PHY) Devices
28250-DSH-002-C
2.4.2.3 Cell Screening
The CX28250 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 the incoming bits to the values in the receive cell
header registers. Cells are rejected or accepted based on the bit patterns of their
headers.
set to 1, all incoming cells that match the contents of the Receive Idle Cell Header
Control registers, RXIDL1-4 (0x2C-2F), are rejected. Individual bits in the
Receive Idle Cell Mask Control registers, IDLMSK1-4 (0x30-33), can be set to
be treated as matching, regardless of their value. If idle cell rejection is disabled,
cells pass directly to user traffic screening.
cells are compared to the Receive Cell Header Control registers, RXHDR1-4
(0x24-27). Individual bits in the Receive Cell Mask Control registers,
RXMSK1-4 (0x28-2B), can be set to 1 or a don’t care state, 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 (0x08) determines
whether matching cells are rejected or accepted. If it is set to 0, matching cells are
accepted. If set to 1, matching cells are rejected. See
Table 2-14. Cell Screening - Matching
Table 2-15. Cell Screening - Accept/Reject Cell
Receive Cell Mask Bit
Idle cell rejection is enabled in bit 6 of the CVAL register (0x08). If this bit is
User traffic cell screening is similar to idle cell screening in that the incoming
Mindspeed Technologies
Match
Match
Cell
Fail
Fail
0
0
0
0
1
Receive Cell Header Bit
Reject Header
0
1
0
1
0
0
1
1
x
™
Incoming Bit
Table 2-14
Accept Cell
Accept Cell
Reject Cell
Reject Cell
2.0 Functional Description
Result
0
1
0
1
x
2.4 ATM Cell Processor
and
Table
Result
Match
Match
Match
Fail
Fail
2-15.
2-33