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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
203
6.4.4.2.6
This “Read/Write” bit-field allows the user to configure
the Transmit DS3 Framer to automatically generate a
“Yellow Alarm” if the Near-End Receive DS3 Framer
detects a “LOS” (Loss of Signal) Condition.
Writing a “1” to this bit-field enables this feature.
Writing a “0” to this bit-field disables this feature.
FERF on LOS—Bit 2
6.4.4.2.7
This “Read/Write” bit-field allows the user to configure
the Transmit DS3 Framer to automatically generate a
“Yellow Alarm” if the Near-End Receive DS3 Framer
detects an “OOF (Out-of-Frame) Condition”.
Writing a “1” to this bit-field enables this feature.
Writing a “0” to this bit-field disables this feature.
FERF on OOF—Bit 1
6.4.4.2.8
This “Read/Write” bit-field allows the user to configure
the Transmit DS3 Framer to automatically generate a
“Yellow Alarm” if the Near-End Receive DS3 Framer
detects an AIS (Alarm Indication Signal) Condition.
Writing a “1” to this bit-field enables this feature.
Writing a “0” to this bit-field disables this feature.
FERF on AIS—Bit 0
6.4.4.3
The TxOH Serial Input port allows the user to insert
his/her value(s) for the OH bits into the outbound
DS3 frames. The TxOH Serial Input port is activated
when the user asserts the TxOHIns pin (e.g., toggles
this input pin “high”). Once this serial port is activated,
then the user is expected to serially apply his/her
Using the TxOH Serial Input Port
choices for the DS3 OH bits at the TxOH input pin.
The TxOHClk output pin functions as a clock that will
sample and latch the data at the TxOH input pin on
its rising edge. The frequency of this TxOHClk clock
signal is approximately 526 kHz. The TxOHFrame
output signal is provided to inform the user when the
value for the first X-bit, within the DS3 M-Frame, is
expected. The TxOH Serial Input port expects the
user to apply his/her value for OH bits in the order
as presented in Figure 48. Specifically, when the
TxOHFrame output pin pulses “high”, the TxOH
Serial Input Port will be expecting the first “X”-bit (of
F-Frame #1). On the very next clock pulse (TxOHClk),
the TxOH Serial Input Port will be expecting the
user’s value for the “F1” bit, and so on.
The TxOH Serial Input port also allows the user to
selectively externally insert his/her value for the DS3
OH data (e.g, allowing some of the OH bits to be
internally generated, while inserting his/her own values
for the remaining overhead bits). This can be accom-
plished by “keeping track” of the number of clock
pulses occurring since the last assertion of the TxO-
HFrame signal, and by asserting the TxOHIns, at the
time the TxOH serial input port would be expecting
the “OH bit(s) that are to be externally inserted”. The
TxOHIns input should be negated for the remainder
of the “M-Frame” sampling period, so that these OH
bits will be internally generated.
Figure 53 presents a timing diagram that illustrates
the behavior of the TxOH serial interface signals dur-
ing user input of the DS3 OH bits.