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CH1794

HIGH SPEED Modem and FAX FAMILY

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

2. To switch to data mode, switch local voice source

from T1:

(a) At the Originate Modem, enter: ATX1<CR>

(b) At the Answer Modem, enter: ATA<CR>

3. To disconnect (hang-up) a voice call or data call:

(a) Return to control mode by entering: +++

(b) Enter: ATH<CR>

4. To place a voice call using the HS Modem DTMF

facilities:

(a) Enter: ATDT1234567<CR>

Where 1234567 is the phone number

(b) Then switch to local voice source

MODEM CONTROL

The HS Modem may be controlled by sending serial

ASCII command sequences. The commands are sent

to the modem serially on the TXD pin. After execution

of a received command, the modem returns a serial

status message that completion status. Refer to Table

5A, 5B and 5C for a complete list of status messages.

MODEM STATES

The HS Modem can be in either command mode or

data mode. When the modem is idle, it is in command

mode by default and will recognize commands. When

data transmission is in progress, the HS modem is in

the data mode state and will not recognize commands.

To force the HS Modem to recognize commands, the

host must send an “escape sequence” to the HS

Modem forcing it out of data mode and into command

mode.

ANALOG VOICE

INJECTED SIGNALS

T1

TIP

RING

High Speed Modem and FAX Family

The escape sequence consists of a “guard time” (a

period where no characters are sent to the modem),

followed by 3 escape characters, followed by a second

guard time. At power-up, the guard time is set to 1

second, and the escape character is set as ”+.” Note

that a 50 msec delay is required between escape

characters. These two parameters can be modified

via registers S2 and S12, respectively.

The HS modem will stay off-hook with its carrier on

after the escape sequence is received. The HS

Modem will return an OK status message when it is

ready to accept commands. To put the HS Modem

back into data mode, issue command ATO<CR>.

THE COMMAND FORMAT

HS Modem commands consist of three elements:

1. The attention sequence,

2. The commands themselves and

3. A terminating carriage return.

Enter: ATDT1234567<CR>

Result: Modem goes off-hook and tone dials phone

number 1234567.

WARNING

The HS Modem family of products has been FCC

Part 68 approved as data/FAX modems. Utilization

of the Voice/Tone Port requires further registration.

The FCC requires that the entire system, including

the HS Modem and the handset or DTMF

transceiver, adhere to Part 68 rules.

RJ-11

JACK

V.24

EIA-232-E

INTERFACE

OR

UART

RXD

DCD

DSR

RI

CTS

TXD

DTR

HS MODEM

FAMILY

EXTERNAL RESET

RST

+5V

GND

SPK

SPEAKER

CONTROL

NOTE: SPEAKER CONTROL AND PHONE

CONTROL ARE ANCILLARY CIRCUITS

SHOWN ELSEWHERE IN THIS DATA SHEET.

*SIGNAL GND MUST BE CONNECTED TO

EARTH GROUND

Vcc

RI

10K

.1uF

3

8

+1

2-

LM393

4

4.7uF

10K

22K

LM393

5

6+

-

Vcc

4.7K

7

Isolated

Envelope

Ring Detect

Figure 4. HS Modem Family Application Diagram.

2003 Cermetek Microelectronics, Inc.

Page 5

Document No. 607-0003 Revision K3 (09/03)

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