TP3420AV datasheet(14/32 Pages) NSC

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Functional Description (Continued)

DIGITAL INTERFACE FORMATS

DIF1)

DIF2)

DIF3)

DIF4)

These instructions select the format of the

Digital Interface timing, see

Figure 3 and

Figure 4.

BCLK FREQUENCY SETTINGS

BCLK1

BCLK2

BCLK3

BCLK4

These instructions change the frequency of a

selected Digital Interface Format. They

should only be used after the Digital

Interface Format has been selected.

However, if another DIF command is applied

after this command, it will override the BCLK

setting.

The default BCLK settings for the DIF

formats are as follows:

DIF1→BCLK1

DIF2→BCLK2

DIF3→BCLK3

DIF4→BCLK4

B CHANNEL CONTROL

BDIR)

BEX )

These commands provide for the exchange

of data between the B1 and B2 channels as

it passes through the device, (Note 10).

B1E)

B1D)

B2E)

B2D)

When either or both B channels are

disabled, binary 1s are transmitted on the

line in those B channel bit positions,

regardless of data at the Bx input, and the

Br output is TRI-STATE in those bit

positions.

INVB1,

INVB2

NRMB12

These commands allow control over the

polarity of the data transmitted over the B1

and B2 channel. The default or the NRMB12

command sets the data to be operated in

normal mode. See section on operation over

restricted channels.

Note 10: When enabling a B channel in conjunction with the BEX Com-

mand, the channels are referenced at the Digital System Interface, not the

line interface e.g. to connect the B1 slot on the DSI with the B2 slot on the line

interface, use the BEX and B1E commands.

D CHANNEL ACCESS

DREQ1)

DREQ2)

This is a request from Layer 2 device to the

TP3420A (in the TE modes) to attempt to

transmit a D channel message at the S

interface. Use DREQ1 to select the access

priority for a Class 1 message (Q.931

Signaling), or DREQ2 for a Class 2

message.

DACCE)

DACCD)

DACCD is the power-up default condition in

TES mode, and DACCE is the power-up

default condition in TEM mode. The D

channel Access algorithm can be enabled

(by DACCE) or disabled (DACCD) in both

TES mode or TEM mode. The D support a

passive bus network lines. The DENx pin

signal provides the flow control strobe

according to the access algorithm.

DCKE)

This command alters pin signals to provide

direct D-channel flow control with certain

HDLC devices. Pin 8 provides gated (DEN

DTCK, Pin 18 provides gated (DEN

R) DRCK,

and Pin 11 inputs TxD data.

See applications note to interface with

MC68302 for use of this command.

EIE

Enable EOM interrupt.

EID

Disable EOM interrupt.

EBITI,

EBIT0,

EBITNRM

These commands allow control over the

D-Echo bit generated in the NT mode

device. The default state or the EBITNRM

command sets Echo bit to its normal

condition which is to reflect the received D

bit back out to the TEs as the Echo bit. The

EBIT0 command forces the Echo bit to be

set to “0” on every frame going back to the

TEs. The EBITI command forces the

transmitted Echo bit to be inverted from that

which is computed from incoming D bits.

LOOPBACK TEST MODES

Three classes of loopback mode are available on the SID,

selected by writing the appropriate Control instruction.

LBS

This loopback at the system interface loops the two

B channels and the D channel from the B

x input to

the B

r output. It may be set either when the device

is activated, in which case it is transparent (i.e. the

channels are also transmitted to the line), or when

it is deactivated.

LBL1/2 These loopbacks turn each individual B channel

from the line receive input back to the line transmit

output. They may be set separately or together.

LBB1/2 These loopbacks at the Digital System Interface

loop the B1 (LBB1) or the B2 (LBB2) channel data

from the B

x input to the Br output. The Bx input data

is also sent to the line transmit output.

CAL

This command clears all loopbacks.

EXTERNAL SELF-ACTIVATING LOOPBACK

A quick self-test of the device is possible by connecting to-

gether the line sides of the transmit and receive transform-

ers. NTA or NTF mode must be selected, and the device can

then be activated by the normal command sequence (Note

11).

Note 11: This test mode is not possible by direct connection of Lo± and Li±

pins due to incompatible internal bias voltages.

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