XR72L52 Datasheet, PDF (285/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
TABLE 48: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L52
NUMBER OF TXOHENABLE PULSES
0 (Clock edge is coincident with TxO-
HFrame being detected "High”)
1
2
3
4
5
6
7
8
9
10
11
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
XRT72L52
THE XRT72L52?
FAS Signal - Bit 9
No
FAS Signal - Bit 8
No
FAS Signal - Bit 7
No
FAS Signal - Bit 6
No
FAS Signal - Bit 5
No
FAS Signal - Bit 4
No
FAS Signal - Bit 3
No
FAS Signal - Bit 2
No
FAS Signal - Bit 1
No
FAS Signal - Bit 0
No
A Bit
Yes
N Bit
Yes
3. After the Terminal Equipment has waited through the appropriate number of pulses via the TxOHEnable
pin, it should then assert the TxOHIns input signal. Concurrently, the Terminal Equipment should also
place the appropriate value (of the inserted overhead bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the TxOHIns input pin "High" and the value of the TxOH signal
stable, until the next TxOHEnable pulse is detected.
Case Study: The Terminal Equipment intends to insert the appropriate overhead bits into the Transmit
Overhead Data Input Interface (using Method 2) in order to transmit a Yellow Alarm to the remote termi-
nal equipment.
In this case, the Terminal Equipment intends to insert the appropriate overhead bits, into the Transmit Over-
head Data Input Interface such that the XRT72L52 will transmit a Yellow Alarm to the remote terminal equip-
ment. Recall that, for E3, ITU-T G.751 applications, a Yellow Alarm is transmitted by setting the A bit to “1".
If one assumes that the connection between the Terminal Equipment and the XRT72L52 is as illustrated in
Figure 103 then, Figure 104 presents an illustration of the signaling that must go on between the Terminal
Equipment and the XRT72L52.
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