CMX624 데이터 시트보기 (PDF) - MX-COM Inc

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CMX624

Bell 202 and V.23 Modem with Call Progress and DTMF

MX-COM Inc  

Bell 202 and V.23 Compatible Modem

10

CMX624 Preliminary Information

4.8 Rx Energy and 2100Hz Detector

The Rx Energy and 2100Hz Detector functional blocks are controlled by Bit 4 and Bit 5 of the FSK MODE

Register and Bit 0 of the TX TONES Register.

This block will measure the frequency and amplitude of the incoming signal when Bit 0 of the TX TONES

Register and Bit 4 and Bit 5 of the FSK MODE Register are set to ‘1’. When a signal of 2100Hz is present

and of sufficient amplitude and time, Bit 4 of the FLAGS Register is set high. See Section 6.1 for amplitude,

time and frequency limits.

When Bit 0 of the TX TONES Register is set to ‘0’, this block compares the signal level at the output of the

Receive Filter against an internal threshold. This may be used as a FSK level detector or a simple Call

Progress Signal detector, according to the settings of Bit 4 and Bit 5 of the FSK MODE Register, which affect

the Receive Filter pass band as described in Section 4.5.

The required register settings are summarized in Table 5.

TX TONES Reg

Bit 0

0

0

0

1

FSK MODE Reg

Bit 5

Bit 4

0

0

1

0

1

1

1

1

Detection Mode

Call Progress

75 / 150bps FSK

1200bps FSK

2100Hz

Table 5: Required Register Settings

Bit 4 of the FLAGS Register is set to ‘1’ by the output of this block when the received level has exceeded the

threshold for sufficient time. Amplitude and time hysteresis, are used to reduce chattering in marginal

conditions. See Section 6.1.

Received

Line Signal

B4 of FLAGS TeON

Register

FSK or Call Progress Signal

TeOFF

Figure 8: Rx Energy Detector Timing

4.9 FSK / DTMF Modulator

When Bit 7 of the TX TONES Register is set to ‘0’ then the FSK/DTMF Modulator generates FSK signals as

determined by Bit 0 and Bit 1 of the FSK MODE Register and the Tx data bits from the UART block as shown

in Table 6 and Table 7.

4.9.1 V.23 mode (Bit 7 of SETUP register = ‘0’):

FSK MODE

Reg

Bit 1 Bit 0

0

x

1

0

1

1

FSK / DTMF Modulator block output

(Bit 7 of TX TONES = ‘0’)

Disabled (output held at VDD/2)

75bps FSK

1200bps FSK

FSK Signal Frequency

‘0’ (Space) ‘1’ (Mark)

450Hz

2100Hz

390Hz

1300Hz

Table 6: V.23 mode (Bit 7 of SETUP register = ‘0’)

©1999 MX-COM, Inc.

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480180.108

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA

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