TP3420AV National Semiconductor, TP3420AV Datasheet - Page 21

• Manufacturer Part Number: TP3420AV
• Manufacturer: National Semiconductor

Specifications of TP3420AV

• Number Of Line Interfaces: 1
• Control Interface: HDLC
• Package Type: PLCC
• Lead Free Status / Rohs Status: Not Compliant

Functional Description
BIPOLAR VIOLATION DETECTION AND FECV
MESSAGING VIA THE SC1 CHANNEL
NT Mode
A Receive Multiframe Error (RMFE) detector circuit in the
TP3420A identifies any multiframes in which one or more bi-
polar violations is received, indicating a bit in error. If one or
more line code violation errors occur in a received multi-
frame (5 ms), the TP3420A generates the RMFE (Receive
Multiframe Error) interrupt. The microcontroller has to send
the Far End Code Violation, FECV (1110) word over the SC1
channel through the MFT1H register. The FECV message is
then sent once, after which the SC1 channel reverts to send-
ing the message from the MFT1L register.
The RMFE circuit detects frame code violations in 16 frames
(out of 20 frames in the multiframe) not containing the multi-
frame Q bit data and detects correct DC balancing in all 20
frames, including the frames containing the multiframe data.
The RMFE detector is operational whether multiframing
messaging is used or not. The RMFE interrupt is disabled by
default on power-up. It is normally enabled after activation is
completed by writing the ENINT command.
TE Mode
When the TE end device receives an FECV message in the
SC1 channel, it is validated on a single occurrence, and the
device generates the MFR1.
If one or more line code violation errors occur in the received
multiframe, the device will generate the RMFE interrupt. The
microcontroller may then keep a count of frame errors being
received. Currently, there is no provision in T1-605 for in-
forming the NT about the errors received at the TE end.
The RMFE circuit detects frame code violations as well as
DC balancing in all 20 frames in the multiframe. In the TE re-
ceived frames, the S bit (for SC1, SC2, etc.) is independent
of the auxiliary framing pulses. The RMFE detector is opera-
tional whether multiframing messaging is used or not. The
RMFE interrupt is disabled by default on power-up. It is nor-
mally enabled after activation is completed by writing the
ENINT command.
(Continued)
21
Applications Information
While the pins of the TP3420A SID are well protected
against electrical misuse, it is recommended that the stan-
dard CMOS practice of applying GND to the device before
any other connections are made should always be followed.
In applications where the printed circuit card may be plugged
into a hot socket with power and clocks already present, an
extra long ground pin on the connector should be used.
To minimize noise sources, all ground connections to each
device should meet at a common point as close as possible
to the GND pin in order to prevent the interaction of ground
return currents flowing through a common bus impedance. A
decoupling capacitor of 0.1 µF should be connected from
this common point to V
the following ways will help prevent noise injection into the
receiver front-end and maximize the transmission perfor-
mance:
1. keep the crystal oscillator components away from the re-
2. keep the connections between the device and the com-
3. keep the connections between the device and the trans-
Figure 6 shows a typical application of the TP3420A in an
ISDN Terminal.
For more in-depth information on a variety of applications,
Application Note AN665 is a comprehensive guide to the
hardware and software required to meet the I.430 interface
specification. Performance measurements, demonstrating
compliance with I.430 and ANSI transmission requirements,
are also included. For additional information on firmware for
the maintenance message channels see Appendix A of this
datasheet.
ceiver inputs and use a shielded ground plane around
these components.
ponents on the L
should be connected close to the device pins.
formers short.
CC
i
±
. Taking care with the pcb layout in
inputs short; the L
i
− capacitors
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