XRT74L74 Datasheet, PDF (421/498 Pages) Exar Corporation – 4 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L74
4 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.1.1
TABLE 91: 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 XRT74L74
NUMBER OF TXOHENABLE PULSES
30
31
32
33
34
35
36
37
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
XRT74L74
THE XRT74L74?
TR Byte - Bit 1
Yes
TR Byte - Bit 0
Yes
MA Byte - Bit 7 (FERF)
Yes
MA Byte - Bit 6 (FEBE)
Yes
MA Byte - Bit 5
Yes
MA Byte - Bit 4
Yes
MA Byte - Bit 3
Yes
MA Byte - Bit 2
Yes
MA Byte - Bit 1
Yes
MA Byte - Bit 0
Yes
NR Byte - Bit 7
Yes
NR Byte - Bit 6
Yes
NR Byte - Bit 5
Yes
NR Byte - Bit 4
Yes
NR Byte - Bit 3
Yes
NR Byte - Bit 2
Yes
NR Byte - Bit 1
Yes
NR Byte - Bit 0
Yes
GC Byte - Bit 7
Yes
GC Byte - Bit 6
Yes
GC Byte - Bit 5
Yes
GC Byte - Bit 4
Yes
GC Byte - Bit 3
Yes
GC Byte - Bit 2
Yes
GC Byte - Bit 1
Yes
GC Byte - Bit 0
Yes
3. After the Terminal Equipment has waited through
the appropriate number of pulses via the TxO-
HEnable pin, it should then assert the TxOHIns
input signal. Concurrently, the Terminal Equip-
ment 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
419