XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
224
The following table relates the contents of this bit-
field to the “OOF Declaration” criteria
Note:
Once the Receive DS3 Framer has declared an
“OOF” condition, it will transition back to the “F-Bit Search”
state within the “DS3 Frame Acquisition/Maintenance”
algorithm (per Figure 68).
In addition to selecting an “OOF Declaration” criteria
for the F-bits, the user has two options for configuring
the “OOF Declaration” criteria based upon M-bits.
1.
M-bit errors do not cause a “OOF” Declaration, or
“OOF” will be declared if 3 out of 4 consecutive
M-bits are in error.
2.
The user will select between these two options by
writing the appropriate value to Bit 0 (M-Sync Algo) of
the Receive DS3 Configuration and Status Register;
as depicted below.
The following table relates the contents of this Bit
Field to the M-Bit Error criteria for Declaration of OOF
The “Framing on Parity” Option
Finally, the UNI offers the “Framing on Parity” option,
which also effects the “OOF Declaration” criteria. As
was mentioned earlier, the UNI allows the user to
configure the Receive DS3 Framer to detect ‘valid-
parity’ before declaring itself “In-Frame”. This same
selection allows the Receive DS3 Framer to also de-
clare an “OOF Condition” if a P-bit error is detected in
2 of the last 5 M-frames.
Whenever the Receive DS3 Framer declares “OOF”
after being in the “In-Frame” State the following will
happen.
The Receive DS3 Framer will assert the RxOOF
output pin (e.g., toggles it “high”).
Bit 4 of the Rx DS3 Configuration and Status
Register will be set to “1” as depicted below.
T
ABLE
47: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENTS
OF
B
IT
1 (F-S
YNC
A
LGO
)
WITHIN
THE
R
X
DS3
C
ONFIGURATION
AND
S
TATUS
R
EGISTER
,
AND
THE
RESULTING
“F-
BIT
OOF D
ECLARATION
CRITERIA
”
FOR
THE
R
ECEIVE
DS3 F
RAMER
F-S
YNC
A
LGO
(B
IT
1)
OOF D
ECLARATION
C
RITERIA
0
“OOF” is declared when 6 out of 16 consecutive F-bits are in error.
1
“OOF” is declared when 3 out of 16 consecutive F-bits are in error.
Rx DS3 Configuration and Status Register, (Address = 0Eh)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Rx AIS
Rx LOS
Rx Idle
Rx OOF
Int LOS
Disable
Framing on
Parity
F-Sync
Algo
M-Sync
Algo
RO
RO
RO
RO
R/W
R/W
R/W
R/W
T
ABLE
48: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENTS
OF
B
IT
0 (M-S
YNC
A
LGO
)
WITHIN
THE
R
X
DS3
C
ONFIGURATION
AND
S
TATUS
R
EGISTER
,
AND
THE
RESULTING
“M-B
IT
OOF D
ECLARATION
C
RITERIA
”
FOR
THE
R
ECEIVE
DS3 F
RAMER
MS
YNC
A
LGO
OOF D
ECLARATION
C
RITERIA
0
M-Bit Errors do not result in the declaration of “OOF”
1
“OOF” is declared when 3 out of 4 M-bits are in error.
Rx DS3 Configuration and Status Register, (Address = 0Eh)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Rx AIS
Rx LOS
Rx Idle
Rx OOF
Int LOS Disable
Framing on Parity
F-Sync Algo M-Sync Algo
X
X
X
1
X
X
X
X