V23 / Bell 202 Modem

CMX624

 2003 CML Microsystems Plc

21

D/624/7

DTMF Transmitter

Notes

Min.

Typ.

Max.

Unit

Level at TOP pin; tones in High Group

4

-1.0

0.0

+1.0

dBm

Twist (level of High Group tones WRT level of

Low Group tones)

-

+2.0

-

dB

Tone frequency accuracy (worst case)

-0.5

-

+0.5

%

Tx Filter and Output Buffer

Notes

Min.

Typ.

Max.

Unit

Change in level at TOP pin caused by changing

bit 2 of FSK MODE Register

2.5

3.0

3.5

dB

Buffer output signal swing;

Load greater than 500

Ω.

5

2.2

-

-

Vp-p

Notes:

5.

FSK Demodulator and Rx UART

Notes

Min.

Typ.

Max.

Unit

Valid Input Level Range

6

-43.0

-

-9.0

dBm

Acceptable Twist (Mark level WRT Space level)

-7.0

-

+7.0

dB

Acceptable Signal to Noise Ratio

7

20.0

-

-

dB

Rx 1200bits/sec (V.23 mode)

Acceptable Rx Data Rate

8

1188

1200

1212

Baud

Mark (Logical 1) Frequency

1280

1300

1320

Hz

Space (Logical 0) Frequency

2068

2100

2132

Hz

Rx 75bits/sec (V.23 mode)

Acceptable Rx Data Rate

8

TBD

75

TBD

Baud

Mark (Logical 1) Frequency

TBD

390

TBD

Hz

Space (Logical 0) Frequency

TBD

450

TBD

Hz

Rx 1200bits/sec (Bell 202 mode)

Acceptable Rx Data Rate

8

1188

1200

1212

Baud

Mark (Logical 1) Frequency

1180

1200

1220

Hz

Space (Logical 0) Frequency

2168

2200

2232

Hz

Rx 150bits/sec (Bell 202 mode)

Acceptable Rx Data Rate

8

TBD

150

TBD

Baud

Mark (Logical 1) Frequency

TBD

387

TBD

Hz

Space (Logical 0) Frequency

TBD

487

TBD

Hz

Notes:

6.

the voltage gain of the Rx Input Amplifier should be adjusted by selecting the appropriate

external components as described in Section 1.6.1.

7.

Flat noise in 300-3400 Hz band for V.23, 200-3400 Hz for Bell 202.

8.

Set by Rx UART and Xtal frequency.

2100Hz Detector

Notes

Min.

Typ.

Max.

Unit

‘Will Decode’ Frequency Range

2040

-

2235

Hz

‘Will Not Decode’ Frequency Range

<2010

-

>2265

Hz

‘Off’ to ‘On’ time

9

-

-

25

ms

‘On’ to ‘Off’ time

9

4.0

-

-

ms

Notes:

9.

2100Hz detection requires a signal within the amplitude range given in the Rx Energy

Detector section.