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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
243
The Receive PLCP Processor will indicate its transi-
tion to the “Out-of-Frame” mode by
Asserting the RxPOOF pin (Note: the RxPLOF
pin will still remain negated).
Asserting the “POOF” status bit in the Rx PLCP
Configuration/Status Register.
Generating a “Change of OOF” status interrupt
request to the local μC/μP
1.
2.
3.
If the Receive PLCP Processor is able to regain Frame
Synchronization, it will negate the RxOOF output pin
and “POOF Status” bit-field in the “Rx PLCP Configu-
ration/Status Register. The Receive PLCP Processor
will also alert the local μP/μC of this occurrence by
generating the “Change in OOF Condition” interrupt.
The user can determine the framing state that the
Receive PLCP Processor is operating in by reading
bits 1 and 2 of the Receive PLCP Configuration
Status Register. The bit-format of this register is
presented below.
Bit 1—PLOF Status
A “1” in this bit-field indicates a “Loss of Frame” status.
Consequently, the Receive PLCP Processor will be
operating in the “Un-framed” state. Conversely, a “0”
in this bit-field indicates that the Receive PLCP
Processor is either in the “In-Frame” or “Out-of-
Frame” state.
Note:
the state of this bit-field (and the RxLOF output pin)
is controlled by the contents of an Up/Down Counter. This
counter is incremented whenever the “POOF Status” bit is
“1” and is decremented when the “POOF Status bit is ‘0’.
However, the counter is decremented at 1/12th of the rate
that it is incremented. Therefore, when the Receive PLCP
Processor goes into the “OOF” condition, this Up/Down
Counter will increment. If the Receive PLCP Processor
requires 1ms to regain Frame-Synchronization, the PLOF
bit-field might very well be asserted, denoting an “LOF con-
dition”. However, even after the Receive PLCP Processor
has declared itself “In-Frame”, the PLOF bit-field will not be
negated until the POOF bit-field has been negated for 12 ms.
Bit 2—POOF Status
A “1” in this bit-field indicates an “Out-of-Frame”
condition. This condition necessarily indicates that
the Receive PLCP Processor is not in the “In-frame”
condition. Therefore, the user will have to read-in the
value of bit 1 in order to determine if the Receive
PLCP Processor is operating in the “Out-of-Frame” or
“Un-Framed” state.
The following table relates the “read-in” values for
bits 1 and 2 to the framing state of the Receive PLCP
Processor.
7.2.2.1.4
The UNI allows the user to force the Receive PLCP
Processor into the “OOF” mode, via software
Reframe via Software Command
command. The user can accomplish this by writing a
“1” to Bit 3 in the Rx PLCP Configuration/Status
Register, as depicted below.
Rx PLCP Configuration/Status Register (Address = 44h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
Reframe
POOF Status
PLOF Status
Yellow Status
RO
RO
RO
RO
R/W
RO
RO
RO
T
ABLE
52: T
HE
R
ELATIONSHIP
BETWEEN
THE
LOGIC
STATES
OF
THE
POOF
AND
PLOF
BIT
-
FIELDS
,
AND
THE
CORRESPONDING
R
ECEIVE
PLCP F
RAMING
S
TATE
POOF B
IT
2
PLOF B
IT
1
R
ECEIVE
PLCP F
RAMING
S
TATE
0
0
In-Frame
0
1
In-Frame—PLOF is still “1” during the “12 ms period” that POOF is “0”
1
0
Out of Frame
1
1
Un-frame