MX604 查看數據表（PDF） - MX-COM Inc

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MX604

v.23 Compatible Modem

MX-COM Inc  

v.23 Compatible Modem

6

MX604 PRELIMINARY INFORMATION

4.2 Mode Control Logic

The MX604's operating mode is determined by the logic levels applied to the M0 and M1 input pins:

M1

M0

0

0

0

1

1

0

1

1

Rx Mode

Tx Mode

1200bps

75bps

off

1200bps

1200bps

off

'Zero-Power'

Data Retime[1]

Rx

Tx

Rx

-

[1] If enabled.

Note: On applying power to the device the mode must be set to 'ZP', i.e. M0=1, M1=1, until VDD has

stabilized.

In the 'Zero-Power' mode, power is removed from all internal circuitry. When leaving 'Zero-Power' mode there

must be a 20ms delay before any Tx data is passed to, or Rx data read from, the device to allow the bias

level, filters and oscillator to stabilize.

4.3 Rx Input Amplifier

The Rx Input Amplifier is used to adjust the signal received to the correct amplitude for the FSK receiver and

Energy Detect circuits (see section 5.1).

4.4 Receive Filter and Equalizer

The Receive Filter and Equalizer is used to attenuate out of band noise and interfering signals, especially the

locally generated 75bps transmit tones which might otherwise reach the 1200bps FSK Demodulator and

Energy Detector circuits. This block also includes a switchable equalizer section. When the RXEQ pin is low

the overall group delay of the receive filter is flat over the 1200bps frequency range. If the RXEQ pin is high

the receive filter's typical overall group delay will be as shown in Figure 3.

0.025

0

-0.025

-0.05

-0.075

-0.1

-0.125

-0.15

500

1000

1500

Frequency/Hz

2000

2500

Figure 3: Rx Equalizer Group Delay (RXEQ = 1) with respect to 1700Hz

1998 MXCOM, INC.

Tele: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480152.004

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