TP3420AN308 National Semiconductor, TP3420AN308 Datasheet - Page 16

• Manufacturer Part Number: TP3420AN308
• Description: IC INTERFACE DEVICE ISDN 20-DIP
• Manufacturer: National Semiconductor

Specifications of TP3420AN308

• Applications: *
• Interface: *
• Voltage - Supply: *
• Package / Case: 20-DIP (0.300", 7.62mm)
• Mounting Type: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *TP3420AN308

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Functional Description
3. Contiguous B1+B2 (128 kbit/s) digital loopback (LBB1,
4. Contiguous B1+B2+D (144 kbit/s) digital loopback (LBD)
5. B1 line loopback (using LBL1) with any FSa/FSb rela-
6. B2 line loopback (using LBL2) with any FSa/FSb rela-
7. Contiguous B1+B2 (128 kbit/s pipe) line loopback
Note that a line loopback for the D channel is not specified in
the CCITT I.430 or the T1-605 specification, to ensure that D
channel signaling is transparently passed end-to-end.
ACTIVATION/DEACTIVATION: TP3420A IN NT MODE
Activation (i.e. transmission and loop synchronization) may
be initiated from either end of the loop.
Activation initiated from the NT: to initiate Activation from the
NT, the TP3420A must be powered up, using a PUP com-
mand, followed (Note 12) by an AR instruction to the Control
Register. Network timing, i.e., an 8 kHz input to FS
present at this time. The device then begins to send data
framed as INFO 2 type, in which bits in the B, D and D-echo
channels are set to binary 0. These frames are detected by
the TE, which replies with data framed as INFO 3 type, syn-
chronized to received frames. A flywheel circuit in the
TP3420A NT searches for 3 consecutive correctly formatted
receive frames to acquire frame synchronization. If Multi-
framing is enabled (MIE), 60 correct frames (3 multiframes)
are required to achieve full loop synchronization. When it is
correctly in sync with received frames, the NT interrupts the
control processor with Status Indication type AP. A second
AR command is required to cause the NT to send INFO 4
frames, in which the B and D channels are enabled for trans-
mission; Status Indication type AI is then set, and the INT
output is pulled low to indicate Activation complete.
Note 12: A delay of 2 msecs is recommended to ensure that all internal cir-
cuits have settled.
Activation initiated by a TE: when Activation is initiated by a
TE, the TP3420A in NT mode will detect the incoming INFO
1 signal and, if it is powered-down will pull the LSD pin and
INT low, either of which can be used to “wake-up” a micro-
processor. A PUP command must then be written to
power-up the TP3420. Upon identifying the INFO 1 signal,
the device will set Status Indication type AP and pull INT low
to indicate that Activation is pending. No INFO 2 frames will
be transmitted until a Control instruction type AR is written to
the device, which allows the Activation sequence to proceed
as described above.
Once Activated, loss of frame alignment is assumed by the
TP3420A when a time which is equivalent to three frames
has passed without it detecting any of the valid pairs of line
code violations which obey the framing rule. If the NT does
detect alignment loss it will start to transmit INFO 2. At this
point the Error Indication (EI) primitive is set, the INT output
is pulled low and the receiver searches to identify the incom-
ing signal and attempt to re-acquire loop synchronization. If
it successfully re-establishes synchronization with the in-
coming signal (INFO 3 frames), a further interrupt is gener-
LBB2) in TEM mode and in NT/TES modes if FSa is
phase synchronous with FSb.
in TEM mode and in NT/TES modes if FSa is phase syn-
chronous with FSb.
tionship in all TE or NT modes.
tionship in all TE nor NT modes.
(LBL1, LBL2) with equal delay, available in TEM mode,
and in NT/TES modes if FSa is phase synchronous with
FSb.
(Continued)
a
, must be
16
ated with Status Indication type AI and re-activation can be
completed by sending an AR command. If, however, the re-
ceiver subsequently identifies that the incoming line signal
has ceased, i.e. INFO 0 is being received, Status Indicator EI
is set and INT pulled low, with the transmitted frames
changed to INFO 2. Deactivation can then be completed by
a DR command, following which Status Indication type DI is
set and the INT output pulled low to indicate De-activation.
If required, a PDN instruction may be written to the Control
Register to power-down the device and enable the LSD out-
put.
I.430 recommends 2 timers should be available in an NT. An
Activation Request to the TP3420A should be associated
with the start of an external Timer 1, if required. Timer 1
should be stopped when the AI interrupt is generated follow-
ing successful Activation. If Timer 1 expires before AI is gen-
erated, however, Control Instruction type DR should be writ-
ten to the device to force de-activation. Timer 2, which is
specified to prevent unintentional reactivation, is not required
since the TP3420A can uniquely recognise INFO 1 frames.
ACTIVATION/DEACTIVATION: TP3420A IN TE MODE
Activation initiated by the TE: to activate the loop with the
TP3420A at the TE end the device must first be powered-up
by a PUP command, followed (Note 3) by a Control Instruc-
tion type AR, which is the Activation Request to begin trans-
mission of INFO 1 frames after verifying that INFO 0 is being
received from the NT. INFO 1 is a continuous pattern of 0+,
0−, and 6 ‘1’s repeated. At this point the TE is running from
its local oscillator and is not receiving any sync information
from the NT. When the NT recognises this “wake-up” signal,
it begins to transmit INFO 2, synchronized to the network
clock (following activation of the “U” interface, if applicable).
This enables the phase-locked loop in the TE’s receiver to
correctly identify bit timing from the NT and to synchronize its
own transmission to that of the NT. On identifying INFO 2 for
3 consecutive frames, the TE changes its transmit data to
INFO 3 and awaits the return of INFO 4 from the NT. Identi-
fication of INFO 4 completes the Activation sequence, so
Status Indication type AI is set, and the INT output pulled
low.
Activation initiated from the NT: when Activation is initiated
by the NT, if the TP3420A in TE mode is powered down, it
will pull the LSD pin and INT low on receiving a line signal.
Either of these can be used to “wake-up” a microprocessor.
A PUP command is required to enable the device to
power-up, identify the received signal, and acquire bit and
frame synchronization. Once INFO 2 has been identified, the
TP3420A will pull INT low, with Status Indication type AP set,
to alert the microprocessor that Activation is pending. The
microprocessor must respond by writing Control Instruction
type AR in order for Activation to proceed. INFO 3 frames are
then transmitted. Finally, an AI Status Indication interrupt is
generated when the NT replies with INFO 4 frames.
As in NT mode, once Activated, loss of frame alignment is
assumed by the TP3420A when a time equivalent to three
frames has passed without it detecting any of the valid pairs
of line code violations which obey the framing rule. If the TE
does detect alignment loss it will cease transmitting immedi-
ately. At this point the Error Indication (EI) primitive is set in
the Status Register, the INT output is pulled low and the re-
ceiver searches to re-acquire loop synchronization if INFO 2
or INFO 4 frames are still being received. If synchronization
is re-established, a further interrupt is generated, with Status
Indication type AI. If, however, the receiver subsequently
identifies that the incoming line signal has ceased, i.e. INFO