TABLE VI Status Register Functions

Byte 2

Indication

76543210

0

0

Line 3 deactivated

0

1

Line 3 line signal present but not in sync

1

0

Line 3 activated bipolar violation (Note 1)

1

1

Line 3 activated no bipolar violation

0

0

Line 2 deactivated

0

1

Line 2 line signal present but not in sync

1

0

Line 2 activated bipolar violation (Note 1)

1

1

Line 2 activated no bipolar violation

0

0

Line 1 deactivated

0

1

Line 1 line signal present but not in sync

1

0

Line 1 activated bipolar violation (Note 1)

1

1

Line 1 activated no bipolar violation

0

0

Line 0 deactivated

0

1

Line 0 line signal present but not in sync

1

0

Line 0 activated bipolar violation (Note 1)

1

1

Line 0 activated no bipolar violation

Note 1

Bipolar Violation does not cause an Interrupt

STATUS REGISTER

Status information for all 4 channels may be read from the

common Status Register by addressing location X FF 2 bits

per line are coded as shown in Table VI A change in the

status of 1 or more lines is indicated by the INT pin being

pulled low provided bit 2 of the corresponding control regis-

ter is set to ‘‘ONE’’ to enable the interrupt for that line

BIPOLAR VIOLATION DETECTOR

On an activated line whenever a line error is received there

will be a violation of the AMI coding rule This is reported by

setting the code 10 for that line The violation indication is

cleared to 11 after a read of the Status Register

As an example of the interpretation of the Status Register

contents if the byte 2 read back from the Status Register

e

the 4 lines line 3 is deactivated line 2 is in sync with no

error since the last read cycle line 1 is in sync but there has

been 1 or more errors since the last read cycle of the Status

Register line 0 is receiving a line signal but the line trans-

mission is not synchronized

Applications Information

POWER SUPPLIES

While the pins of the TP3404 QDASL device are well pro-

tected against electrical misuse it is recommended that the

standard CMOS practice of applying GND to the device be-

fore any other connections are made should always be fol-

lowed 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 the VDDA and VDDD pins

should be connected together via the shortest possible

trace likewise the GNDA and GNDD pins must be connect-

ed together These two connections can be done directly

underneath the part All other ground connections to each

device should meet at a common point as close as possible

to the GNDD pin in order to prevent the interaction of

ground return currents flowing through a common bus im-

pedance A power supply decoupling capacitor of 01 mF

should be connected from this common point to VDDD as

close as possible to the device pins

Figure 5 shows a typical 4 line application of the QDASL

The current list of suitable commercial transformers is

Schott Corporation (Nashville)

Phone 615-889-8800

Part numbers 67110850 (dry)

67110860 (50 mA DC)

Pulse Engineering (San Diego)

Phone 619-674-8100

Part number TBD

Note that the zener diode protection shown in

Figure 8 is

only intended as secondary protection for inside wiring ap-

plications primary protection is also necessary Further in-

formation

can

be

found

in

the

datasheet

for

the

TP340123 DASL devices and in Application Note AN-509

‘‘Using the TP340123 ISDN PBX Transceivers’’

10