User Manual

14 CompactRFTM Operating Manual: Chapter 3 Configuration Options
DATA
MODE
POWER-UP
SEQUENCE
COMMAND
MODE
USER TYPES 'MHX'
5 sec elapses
or
characters
other than
'MHX'
entered by
the user
(ATA or ATO Command)
DTR or
Escape Sequence
Figure 4A. S0=1, S119=1
(factory default)
DATA
MODE
POWER-UP
SEQUENCE
COMMAND
MODE
500 msec
(ATA or ATO Command)
DTR or
Escape Sequence
Figure 4B. S0=1, S119=0
DATA
MODE
POWER-UP
SEQUENCE
COMMAND
MODE
500 msec
(ATA or ATO Command)
DTR or
Escape Sequence
Figure 4C. S0=0
The escape sequence will not
be accepted unless both the
MHX-2400 and the terminal
are set to the same baud rate
The terminal must be set for 9600 baud 8N1 in order for the modem to accept
these characters. If ‘MHX’ is typed incorrectly, the modem will immediately
enter into data mode. If the five seconds elapses without any response from
the user, the modem will go into data mode.
In command mode, the module “autobauds,” meaning that it will adapt to the
baud rate of the DTE equipment to which it is connected. Therefore, when in
command mode, you may change the baud rate of your equipment, and the
MHX-2400 will automatically adjust to this baud rate once an AT string is
issued. The new baud rate is stored in register S102. Several baud rates
ranging from 2400 to 115200 may be selected.
You can place the modem into Data Mode from Command Mode either by:
• Issuing the answer command (ATA <ENTER>); or,
• Issuing the online command (ATO <ENTER>).
The modem will now attempt to communicate with other MHX-2400
modules. While in Data Mode, the modem will communicate through the
serial port at the same baud rate as was last used in Command Mode
2
.
To return to Command Mode, you can either:
• Send the escape sequence. (The escape sequence consists of 1 second of
inactivity, followed by the characters ‘+++’ followed by another second
of inactivity.); or,
• Toggle the DTR line (depending on the &D parameter see pg 11).
The escape sequence must be issued at the baud rate that the modem has been
set to. If the modem is set to 19200 baud, and the escape sequence is issued
at 9600 baud, for example, the modem will not recognize it, and will not go
into Command Mode.
Figure 4 provides a state diagram for power-up, command mode, and data
mode. Note that there are three different variants of the state diagram which
depend on the values of registers S0 and S119. See the appropriate sections
for more details about these registers. The factory defaults are S0=1 and
S119=1.
2
It is possible to enter into Data Mode at a different baud rate from what is
currently being used in Command Mode by issuing the command ATS102=x,
where x is one of the valid baud rates. Care must be taken when setting the
baud rate in this manner. If you issue another AT string after attempting to
set the baud rate using ATS102 <ENTER>, the modem will again autobaud
and automatically revert to the baud rate of the host equipment. For example,
if your equipment is running at 9600 baud and you wish to set up the modem
to run at 19200 baud, the following command line entry would be suitable:
ATS102=5&WA <ENTER>
The first part (S102=5) sets the baud rate to 19200. The next characters
(&W) write this baud rate to memory. The last character (A) puts the modem
into Data Mode. Once in Data Mode, the modem is unable to autobaud, and
is fixed at 19200 baud. By combining several commands into one command
line entry, and then immediately putting the modem online, the modem is not
given a chance to autobaud back to 9600.