OPERATING MODES

The various operating modes are defined by

MC/BC and MOD/DTMF inputs, and by the content

of a control register RPROG.

The TS7514 includes 8 control registers. Access to

each control register is achieved through an auxil-

liary 8-bit shift register (input register). The input of

that shift register is connected either to TxD or

PRD, depending upon the statusof the ENP control

pin (ie when ENP = 0 and ENP = 1 respectively).

In both cases, the RTS input receivesthe shift clock

and sequentialy transfer is controlled by setting

simultaneously MOD/DTMF and MC/BC to 0. The

previous internal status and data are memorized

during loading of the input register so that transmis-

sion continues properly. That feature allows the

user to modify transmission level or line monitoring

selection during transmission. The transmit chan-

nel operatingmode (Modem main or back channel,

DTMF) can only be modified when RTS = 1. When

RTS = 0, the ATO transmit output is enabled and

the preselected operating mode is activated. When

RTS returns to 1, Modem or DTMF transmission is

inhibited after the first zero crossing of the gener-

ated signal.

MOD/DTMF

MC/BC

Transmission (ATO)

Reception (RxD, DCD)

1

1

MODEM, Main Channel

MODEM, Back Channel

1

0

MODEM, Back Channel

MODEM, Main Channel

0

1

DTMF

DCD= Active Tone Detection (270 -500Hz) if RTS = 1

…

DCD = 1 if RTS = 0

0

0

If RTS = 0 when that configuration occurs, transmission and reception are not modified.

If RTS = 1 (no signal sent on the line), transmission is not modified and reception is set

up to detect 2100Hz tone (note 1).

Note 1 : The decision threshold of the demodulator output is shifted, so that RxD changes from 0 to 1 at 1950Hz instead of 1700Hz.

MODEM TRANSMISSION FREQUENCIES

Modulation

Rate

TxD

CCITT R35 AND V.23

Recommendations (Hz)

Frequency Generated with

Xtal at 3.579MHz (Hz)

Error (Hz)

75bps

1

0

390

±2

450

±2

390.09

450.45

+0.09

+0.45

1200bps

1

0

1300

±10

2100

±10

1299.76

2099.12

-0.24

-0.88

DTMF TRANSMISSION FREQUENCIES

Specifications

DTMF (Hz)

Frequency Generated with

Xtal at 3.579MHz (Hz)

Dividing Ratio

Error (%)

f1

f2

f3

f4

f5

f6

f7

f8

697

±1.8%

770

±1.8%

852

±1.8%

941

±1.8%

1209

±1.8%

1336

±1.8%

1477

±1.8%

1633

±1.8%

699.13

771.45

853.90

940.01

1209.31

1335.65

1479.15

1627.07

5120

4640

4192

3808

2960

2680

2420

2200

+0.31

+0.19

+0.22

-0.10

+0.03

-0.03

+0.15

+0.36

TS7514

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