XRT72L53 Datasheet, PDF (174/467 Pages) Exar Corporation – THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

áç THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L53
REV. P1.1.7
TABLE 22: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE TXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
XRT72L53
THE XRT72L53?
DL
Yes
F1
No
M1
No
F1
No
UDL
Yes
FO
No
UDL
Yes
FO
No
UDL
Yes
F1
No
M0
No
F1
No
UDL
Yes
F0
No
UDL
Yes
F0
No
UDL
Yes
F1
No
3. After the Terminal Equipment has waited the
appropriate number of clock edges (from the
TxOHFrame signal being sampled "High"), it
should assert the TxOHIns input signal. Concur-
rently, 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 rising edge of
TxOHClk is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
Method 1) in order to transmit a Yellow Alarm to
the remote terminal equipment.
In this example, the Terminal Equipment intends to in-
sert the appropriate overhead bits, into the Transmit
Overhead Data Input Interface, such that the
XRT72L53 will transmit a Yellow Alarm to the remote
terminal equipment. Recall that, for DS3 Applica-
tions, a Yellow Alarm is transmitted by setting both of
the X bits (within each outbound DS3 frame) to 0.
If one assumes that the connection between the Ter-
minal Equipment and the XRT72L53 are as illustrated
in Figure 57 then Figure 58 presents an illustration of
the signaling that must go on between the Terminal
Equipment and the XRT72L53.
174