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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
173
6.2.2.5
The Transmit Cell Processor provides for some
performance monitoring of the communication link
between the various UNIs, over the “ATM Switching
System”. This performance monitoring feature is re-
ferred to as the “Data Path Integrity Check”.
The Receive Cell Processor, or some equivalent entity,
within a UNI device, will (after performing HEC byte
verification) write a “Data Path Integrity Check” pattern
into each cell prior to its being read and processed by
the ATM Layer processor. This cell (with the “Data
Path Integrity Check” pattern) will be routed through
the ATM switch, and possibly throughout the Wide
Area Network (WAN); before arriving to the Transmit
UTOPIA Interface block of a given XRT7245 DS3
UNI. The Transmit Cell Processor will read in this cell
from the Tx FIFO, and will, prior to inserting a new
Data Path Integrity Check
HEC byte into the cell, read in the fifth octet from the
Tx FIFO and check it for a specific pattern or value.
The user can configure the Transmit Cell Processor
to check for either a constant “55h” pattern or an al-
ternating pattern of “55h” and “AAh” for each cell. The
user can also configure the Transmit Cell Processor
to generate an interrupt if a Data Path Integrity Test
fails. The user can accomplish all of this by writing
the appropriate data to the “Tx CP Control” Register
(Address = 60h). The bit format (with the relevant bit
fields shaded) of this register is shown below.
Note:
1. The “Data Path Integrity Check” feature is disabled
if the Transmit (and Receive) UTOPIA Interface
blocks have been configured to handle 52 byte cells.
2. This “Data Path Integrity Test” is only performed on
user cells. The Transmit Cell Processor does not
perform this test on OAM or Idle Cells.
The role that each of these “shaded” bit field plays is
presented below.
Bit 4—TDPChk Pat—Test Data Path Integrity
Check Pattern
The Transmit Cell Processor is always checking for a
specific pattern in the fifth octet of a user cell re-
trieved from the Tx FIFO. This “Read/Write” bit allows
the user to specify the octet pattern that the Transmit
Cell Processor should be checking for. The following
table relates the contents of this bit field to the octet
pattern expected by the Transmit Cell Processor.
PMON Transmitted Idle Cell Count—LSB (Address = 39h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Tx Idle Cell Count—Low Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Tx CP Control Register (Address = 60h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Scrambler
Enable
Coset
Enable
HEC Insert
Enable
TDPChk
Pattern
GFC Insert
Enable
TDPErr Interrupt
Enable
Idle Cell
HEC CalEn
TDPErr Interrupt
Status
R/W
R/W
R/W
R/W
R/W
R/W
R/W
RUR
T
ABLE
20: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENTS
OF
B
IT
4 (TDPC
HK
P
AT
)
WITHIN
THE
T
X
CP C
ONTROL
R
EGISTER
,
AND
THE
“D
ATA
P
ATH
I
NTEGRITY
C
HECK
” P
ATTERN
THAT
THE
T
RANSMIT
C
ELL
P
ROCESSOR
WILL
LOOK
FOR
IN
THE
5
TH
OCTET
OF
EACH
INCOMING
USER
CELL
TDPC
HK
P
AT
“D
ATA
P
ATH
I
NTEGRITY
P
ATTERN
” E
XPECTED
BY
THE
T
RANSMIT
C
ELL
P
ROCESSOR
0
Transmit Cell Processor expects an alternating “55h/AAh” pattern for the value of the fifth octet of the
cells received from the Tx FIFO.
1
Transmit Cell Processor expects a constant “55h” pattern for the value of the fifth octet of the cells
received from the Tx FIFO.