Using Hyperterminal for Modem Troubleshooting

You can use a standard Windows application called Hyperterminal to perform certain tasks, such as changing a modem’s communication rate.

Note ♦ The modem driver does not need to be installed in order to access the modem via Hyperterminal.

Modem Connections

Using Hyperterminal

Open Hyperterminal. The program can generally be located by clicking the Start button in the lower left corner of your screen, then selecting Programs>Accessories>Communications>Hyperterminal. The New Connection window opens as shown below.
Note ♦ Hyperterminal generally starts by pointing to the internal modem, if one is installed on the PC.

Enter a name for the new connection and select an icon, and then click OK. The Connect To box opens .
Select a COM port for the modem, and then click OK.

The Port Settings box opens as shown below. To enable your PC to communicate with the modem, set the COM port parameters to a BPS of either 9600 or 19200, Data bits=8, Parity=N, Stop bits=1, Flow control=None, and then click OK.

Open the modem’s Properties box by clicking on the Properties button, then open ASCII Setup.

Select the options shown below, and then click OK.

Hyperterminal is now connected to your PC via Com 1; the ASCII settings now enable you to enter commands via the PC keyboard and see the replies from the modem within the Hyperterminal window.

To test the connection, type AT; if the connection is valid the modem will respond 'OK'.

To change the modem’s baud rate, type AT+IPR=19200&W; the command '&W' burns the new baud rate into the modem's non-volatile memory.

Typical initialization strings used with an Siemens M20-type modem are shown below.

Modem Commands

Note ♦ The modem must reply with either OK or READY to each command entered. If the modem fails to answer, the command has not been processed.

+++	Escape Sequence. This causes the modem to close connections and go back to command mode
AT	This command means Attention; and is used to begin a session
AT&F	Restores factory default settings
ATZ	Resets the modem. This command may take time to implement, so the response from the modem may be delayed
ATE0	No Echo
V1	Enable Verbose (long) response
Q0	Respond
X4	Detailed answers
&D0	Ignore DTR
&D2	Once DTR falls, disconnect and go to command mode
&D1	Once DTR falls, disconnect
&S0	DSR always ON. Since the DSR can be permanently set to ON, connecting it to the RTS causes the terminal always be ready to transmit\receive data
&S1	DSR OFF in command and test modes
&C1	Give the user a signal for the DCD
&C0	Don’t give the user a signal for the DCD (refers to LED indications where relevant)
ATS0=1	Auto-Answer after 1 ring
S0=0	Modem doesn't answer. Forces PLC to answer with ATA (pickup)
S10=15	Sets the time ( in units of 0.1 sec) from the time when CD is not detected, until the string NO CARRIER is shown. If the value is 255, then the CD signal will not fall—even if the modems are no longer connected
S7=30	TimeOut: If this time is exceeded, the modem notifies that dial has failed
S12	The modem register that defines the time interval during which the line must remain clear, before and after the +++ command. Note ♦ In the M90, this value is fixed on the M90 side and is not entered into the modem. If the controller cannot hang up, register S12 should be checked to ensure that the pause =1.2 sec
&W	Burn the configuration into the modem’s non-volatile memory

Initializing the modem to SMS mode via Hyperterminal

Once the modem is successfully initialized, you can use Hyperterminal to initialize the modem to SMS mode.

Command	Description	Notes
at+cpin=?	Is a pin number required?
at+pin=”xxxx”	Is the pin number set in the application?	XXXX is the PIN number coming from the U90 application.
at+creg?	Has the SIM card been registered with the local cellular provider?	Should return one of two answers: +CREG: 0,1 The SIM is registered with its local provider. +CREG: 0,5 The SIM is in roaming mode.
at+cmgf=1	Go to text mode

Notes ♦	Commands including question marks are run for verification twice. If the command is not verified during the second attempt, the attempts stop.
♦	If the SIM requests the PUK number, the SIM must be taken out of the modem and installed into a phone to enable the number to be entered.
♦	If the SIM is full, the SIM must be taken out of the modem and installed into a phone to enable the SIM to be cleared.
♦	The modem must be able to support Text mode. P.D.U. mode is not supported.

When a controller sends an SMS text message

The controller uses the Send command, containing the number to be called: AT+CMGS= ”phone number”.
The controller then waits for the reply '>'.
When the '>' is received, the controller sends the message, ending the line with CTRL_Z
If the message is successfully sent, the controller will receive a message of confirmation,+CMGS:xx. When this message is received by the controller, SB 184 turns ON. The confirmation message is acknowledged by OK.
If :
the message of confirmation is not received within 15 seconds, or
the '>' is not received within 3 seconds, SB 185 turns ON.

When the controller receives an SMS text message:

It receives the command: +CMTI: “SM” ,xx. Xx is a number in the controller's memory, 1 to 20.
When the message is received, the controller asks the modem for the text via the command AT+CMGR=xx
The modem replies with +CMGR, including the phone number, status, text, and concluding with OK.

Note ♦

When a Com port has been successfully initialized, the relevant bit turns ON: SB 80 , 82, 83 or 84.
If initialization fails, SB 81, 83, 85, or 87 will turn ON.

'The Sniffer'--Viewing communication strings

The instructions below show you how to construct a communications 'Sniffer'. This device enables you to use Hyperterminal to view communication strings flowing between a PLC and an external, connected device such as a bar code reader.

‘Sniffer’ is connected to the external device.

‘COM’ is connected to the PLC.

The completed Sniffer is connected to a PLC communication port, PC and external device.

Note that communication cables are the programming cable provided by Unitronics.

To make a Sniffer, you need:

An adapter.
Two 1N4148 or 1N914 diodes.

Open the adapter carefully via the 4 snaps in its sides.

Cut the red and green wires as shown below.
Solder one diode to the red wire, and one diode to the green wire. The soldered point provides the anode.
Put isolating material on the soldered points.
Solder both diodes’ cathodes to the red wire.
Put isolating material on the solder. Close the Sniffer. Label the connectors as shown.

Note ♦ In order to run view the strings in Hyperterminal, you must set the program to display ASCII strings as described above in Using Hyperterminal.