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CMX644AP4

Bell 212A and V.22 Modem with Call Progress and DTMF

MX-COM Inc  

Bell 212A / V.22 Modem with Call Progress and DTMF

10

CMX644A Preliminary Information

4.3.2.2 SET-UP Register ($E0)

(Bit 7)

RELAY DRIVE

(Bit 6)

DETECT DET1 and DET0

(Bits 5 and 4)

LOOPBACK L1 and L0

(Bits 3 and 2)

XTAL FRQ X1 and X0

(Bits 1 and 0)

Reserved for future use. This bit should be set to ‘0’.

This bit controls a low impedance pull-down transistor connected to the

RLYDRV pin to assist with the operation of an ‘off-hook relay’. When set to ‘1’

the transistor acts as a pull-down and will sink current. When set to ‘0’ the pin

is in a high impedance state.

These 2 bits control the operation of the receiver filter in order to facilitate the

detection of the following signals as shown in Table 5.

These 2 bits control internal signal paths such that loopback tests can be

performed. Function is according to Table 6.

These two bits control the internal primary clock dividers to allow for a choice of

3 crystal frequencies. They can also be set to put the device into ‘Zero Power’

mode: in this mode all functions are powersaved, except for the ‘C-BUS’ and

the Ring Detector. In ‘Zero Power’ the crystal oscillator is disabled and the Bias

resistor chain is disconnected from the supplies.

Note: When the device is brought out of ‘Zero Power’ mode, the software

should allow at least 20ms for the crystal oscillator to re-start and for the Bias

capacitor to re-charge, before proceeding with any further device functions.

The function is provided according to Table 7.

Table 4: SET-UP Register ($E0)

DET1 (Bit 5)

0

0

1

1

DET0 (Bit 4)

0

1

0

1

Required Rx HI/LO Band Setting

(Register $E8, Bit 0)

As required for Rx PSK

LO = '0'

HI = '1'

As required for Rx PSK

Detection Mode

PSK Carrier

Call Progress

Answer Tone

Detectors OFF

Note: RX PSK MODE register ENABLE bit should be set to '1' for answer tone and call progress detection.

Table 5: DETECT (DET1 and DET0)

L1 (Bit 3)

0

0

1

1

L0 (Bit 2)

0

1

0

1

Normal Device Operation: no loopback.

Local Analog Loopback: the output of the Tx gain block is routed to the input of the

receiver gain block. (The connection between the receiver op-amp and gain block

is broken).

Local Digital Loopback: data is loaded into the TX DATA BYTE register in the usual

way via the ‘C-BUS’ when indicated by the TX DATA READY flag. This digital data

is internally retimed serially to the modem bit-rate and is then clocked into the

receiver buffer. When the receiver buffer is full the RX DATA READY flag will be set

and the data can then be read out of RX DATA BYTE register via the ‘C-BUS’.

Reserved for future use.

Table 6: LOOPBACK L1 and L0

X1 (Bit 1)

0

0

1

1

X0 (Bit 0)

0

1

0

1

Crystal / Mode

‘Zero Power’

3.6864MHz crystal

7.3728MHz crystal

11.0592MHz crystal

Table 7: XTAL FREQ X1 and X0

2000 MX-COM, Inc.

www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054

Doc. # 20480197.006

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

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