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CH2156 Datasheet PDF : 19 Pages
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Figure 5. iModem® Family Application Diagram
®
These commands disable auto-answer and eliminate hang-up due
to lack of carrier signal.
1. Enter: ATS0=0 [CR]
2. Enter: ATS7=255 [CR]
3. Enter: ATS10=255 [CR]
The following command sequences illustrate implementation of com-
mon voice/tone port applications.
1. To answer a voice call:
(a) Enter: ATH1 [CR]
(b) Switch local voice source into RXA and TXA
(c) Begin voice conversation.
2. To switch to data mode, switch local voice source from
RXA and TXA:
(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 facili
ties:
(a) Enter: ATDT(Tele)#;[CR]
(b) Then switch to local voice source
iModem® STATES
The iModem can be in either the Internet State or the Modem
State. Because the iModem® has the unique ability to
operate as either a high speed V.90 Modem or as an internet
email transceiver, the commands sent on TXD (or the status of
the Send Email Control Pin) determine operation.
iModem® Internet State.
The iModem® can be controlled by providing status flags on the
Send Email Control Pin (pin #6) or by sending ASCII commands via
the serial interface. Use of Pin #6 forces Internet email transmis-
sion operation. Upon successful transmission of an EMAIL, the
iModem® sends a momentary 100ms Low going TTL output pulse
on the Email Accepted Pin (Pin #8) indicating the email has been
received by the ISP Mail Server. If desired, a simple latch circuit
(see example in Figure 8) can be used to illuminate an LED to indi-
cate Email Accepted.
This message indicates command completion status. Refer to
Tables 5A, 5B and 5C for a complete list of status messages.
iModem® Modem State.
When in the Modem State, the iModem® 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 trans-
mission is in progress, the iModem® is in the data mode state and
will not recognize commands. To force the iModem® to recognize
commands, the host must send an “escape sequence” to the
iModem® forcing it out of data mode and into command mode.
The escape sequence consists of a “guard time” (a period where no
characters are sent to the modem), followed by 3 escape charac-
ters, followed by another guard time. At power-up, the guard time is
set to 1 second minimum, and the escape character is set as “+”.
These two parameters can be modified via registers S2 and S12,
respectively.
The iModem® will stay off-hook with its carrier on after the escape
sequence is received and it returns an OK status message when it is
ready to accept commands. The HS Modem can be put into data
mode by issuing the command ATO [CR].
THE COMMAND FORMAT
Typical commands consist of three elements:
1. The attention sequence,
2. The commands themselves and
3. A terminating carriage return.
WARNING: the iModem® 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.
AT [commands] [CR].
Where: [AT] represents attention sequence.
[commands] represents command strings.
[CR] represents carriage return (ASCII 13 or HEX 0D).
When entering commands to the modem, the backspace charac-
ter-control-H (ASCII 8 or HEX 08) can be used to edit mistakes.
“AT” and “A/” may not be edited however. Multiple commands may
be placed in the command line. A command line may be as long
as 40 characters, excluding the letters AT.
© 2000 Cermetek Microelectronics, Inc.
Page 5
Document No. 607-0017 Rev. B (06/00)
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