TS7514 查看數據表（PDF） - STMicroelectronics

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TS7514

PROGRAMMABLE V.23 MODEM WITH DTMF

STMicroelectronics 

TS7514

CARRIER LEVEL DETECTOR

- Output Level Detection conditions

The DCD signal detector output is set to logic

state 0 if the RMS value of the demodulator input

signal is greater than N1. The DCD output has

logic state 1 if the RMS value is less than N2.

The detector has an hysteresis effect : N1 - N2.

- Timing Detection Requirements

Signal detection time constants at the DCD out-

put comply with CCITT Recommendation V.23.

Modulation Ratio DCD Transition

1200bps

t1

t2

75bps (Note 1)

t1

t2

Note 1 : wide band Rx filter used (see Figure 7c).

CCITT V.23 (min)

10

5

0

15

Min.

10

5

15

15

Max.

20

15

40

40

CCITT V.23 (max)

20

15

80

80

Unit

ms

ms

ms

ms

Figure 4 : Signal Detection Time Out

N1

N1

LINE

0V

DCD

t1

t2

Note : When delays are bypassed (see RPRX register programming) response time ranges from 0 to 5ms in receive mode at 1200bps,

and from 0 to 10ms at 75bps.

PROGRAMMING REGISTER (RPROG)

Address

Data

D7 D6 D5 D4 D3 D2 D1 D0

Selected Mode (note 1)

X 0 0 0 0 X 0 0 The most significant bit (D7) is not used when decoding control

0 X 1 1 register addresses.

0 X 0 1 Control register addressing is enabled when D7 = 0 (see note 2).

0 X 1 0 Control register addressing is enabled when D7 = 1 (see note 2).

0 0 X X Reception positioned in the channel opposite tothe transmission

channel controlled by MC/BC

0 1 X X Reception positioned in the same channel as transmission

(see note 3).

1 X X X Programming inhibited in normal operating mode. This mode is

used for testing purposes.

Notes : 1. RPROG is set to 0000 on power-up.

2. Excepted for RPROG register whose address is always 000, regardless of D0 and D1.

3. This mode allows either full duplex operation on a 4-wire line, or circuit testing with external Tx/Rx loopback.

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