© 2000 Cermetek Microelectronics, Inc. Page 6
Document No. 607-0017 Rev. B (06/00)
iModem® Training Command Sequence.
The iModem® is trained by sending it the following sequence:
Enter:
AT[CR]
Where: A and T may be either upper or lower case but
must be the same case.
[CR] represents carriage return.
iModem® will respond with one of the following status messages,
depending on whether it is optioned for abbreviated or English
status messages.
Result: 0[CR] (Abbreviated form)
Result: [CR][LF][OK][CR][LF] (English form)
Where: [CR] represents carriage return (ASCII 13 or
HEX 0D)
[LF] represents line feed (ASCII 10 or HEX 0A)
The iModem® is now in idle, the DTE speed is set to a default
speed of 57.6kbs mode and the iModem® is ready to accept
commands.
As an alternate attention sequence “A/” may be sent which
behaves much like the AT sequence except that it causes the
previously entered command specified with an AT prefix to be
executed. When given, it must be in the upper case ASCII. No
carriage return is needed.
Extensions to the basic result code set can be specified by Register
S95, which allows for the use of result codes 40 - 64, 165 - 194.
Note: To obtain a detailed status report for a given modem commu-
nication configuration, use the AT/V1 command. Executing this
command at setup will cause the iModem® to connect and return a
message on line consisting of <DTE speed> <modulation> <error
protocol> <line speed of connection>.
AT COMMAND APPLICATIONS WHEN OPERATING THE
iModem® IN THE INTERNET STATE
Each iModem® is delivered with a pre-programmed ISP account ID
and password, local Sunnyvale, CA, dial-up ISP access phone
number and a default pre-programmed email subject title for use
on an interim basis.
Sending Emails.
If an email is to be sent utilizing the Cermetek pre-programmed
internet configuration profile (i.e., the pre-programmed ISP account
ID and password, and the pre-programmed destination email
address), issuing the @TD command is all that is needed to send
an email.
Example:
Initiate dial-up and complete email
transmission using the pre-programmed
internet configuration profile.
Enter:
@TD
The user may suppress certain subsets of the non-extended
result codes. This is accomplished by selecting subsets of the
result code set using the ATXn command, where n=0, 1, 2, 3.
Optionally, the user may specify an extended set of result codes
(codes above 35) by setting Register S95. See the detailed
description of result codes in Table 5A, Table 5B and Table 5C.
All AT commands, other than dialing commands, will be re-
sponded to with either an OK (short form result code 0) if the
command is valid or accepted, or with an ERROR (result code 4)
if the command is not recognized. The detail contained in the
error result code signaled to the DTE depends on the level of
message suppression employed by the user. As can be seen
from Tables 5A, 5B and 5C, specifying X4 allows the iModem® to
utilize the entire range of non-extended messages, whereas X0
suppresses all but the very basic result codes. Most of the result
codes allowed under X1, X2 and X3 are considered call progress
status codes and, in practice, are suppressed except for the case
of debugging activities. It is recommended that the non-extended
result codes be used in all cases.
It should be noted that the default connect result codes 9-20
indicate DTE connection speed, not Carrier Line DCE speed.
Hence, the iModem® will connect at a maximum speed of
57.6kbps (result code 18) unless the DTE is forced to a higher
speed by selection of data compression. In this case, the
maximum DTE to iModem® speed is 230.4kbps (result code 20).
All result codes have either a terse, short form version (which is
identified by a number followed by a [CR]) or a verbose long form
English-like message version (which is preceded and terminated
with a [CR] and line feed).
INITIALIZING THE iModem®
Before commands may be sent to the iModem®, the iModem®
must be initialized. This consists of two events:
1. Modem Reset. This is accomplished by applying a hardware
reset pulse to pin RST or by switching the power off and then
back on.
2. Initial Modem Training. The modem must be trained to the
host DTE speed and parity (odd, even, mark, space or none).
These activities are briefly described below.
Reset.
Upon applying power to the iModem®, the iModem® automati-
cally generates an internal reset pulse. The user can also reset
the modem externally by applying a high-going reset pulse to the
RST pin for at least 10ms after the +5V power supply has been
stabilized. Delay sending commands to iModem® for 900ms after
reset has been initiated to allow the iModem® time to properly
reconfigure.
On power up, or when reset is initiated either by command ATZ or
by the RST pin, the iModem® will reconfigure to it’s default state
with the line carrier modulation DCE speed set to 56 kbps.
If desired, any speed, error correction, or data compression
method available on the iModem® can be locked in, using the
AT\Nn and/or AT+MS commands.
Training the iModem®.
The iModem® must be trained to match the host DTE speed and
parity so that it is able to recognize serial asynchronous com-
mands sent to it by the DTE.
The DTE must retrain the iModem® each time a reset pulse is
applied on RST or after a RESET serial command has been
issued.
By way of example, the command below instructs the iModem® to
configure itself to not echo characters when in command mode
(E0) and then put itself in answer mode (A).
Enter: ATE0A[CR]
Standard AT Command Set.
The Hayes AT command set is divided into four types of com-
mands: dial modifiers, basic commands, ampersand and percent
commands. Refer to the complete list in Tables 6A and 6B.
STATUS MESSAGES AND RESULT CODES
A result code is issued by the iModem® to the DTE for all
commands executed by the iModem®, except dialing and internet
commands. Further, various activities on the PSTN are also
signaled to the DTE by the iModem®.
