Procedures RS232 Modem Support
ML2437A/38A OM/PM PN: 10585-00001 Rev. P 6-5
Requested data is returned in the same format as with GPIB, but with a preceding 'R' and a
terminating new line character. SRQs are available, and are output as SRQ message 'S'
followed by a terminating new line character. When the SRQ message has been received, an
"!SPL" command (equivalent to the GPIB serial poll) can be issued. The power meter will
respond with the serial poll data message which is a single character preceded by 'P' and
terminated by a new line character.
A device clear message !DCL can be sent to clear the power meter input and output message
queues, and terminate any GPIB or serial actions pending.
At power on, factory reset, in response to the MODINIT command, and after the INIT key in
the modem menu is pressed, the following sequences will be output:
1. +++ath\r\r
2. at&h1&r2x4v1q0f1s0=1e0\r\r
There will be a delay between the two sequences.
These sequences will initialize an attached Hayes-compatible modem. This is the only type of
modem supported.
6-9 RS232 Modem Support
The ML243xA Power Meter can be operated remotely through a modem connected to the rear
pane serial connector (See Chapter 3, Connectors, for the location of the serial connector)
using the GPIB/RS232 command set. The menu selection System > Rear panel > RS232 >
MODE must be set to EXT COMMS.
To initiate communications with the power meter from a remote computer, communications
must be established between the two modems. Once this is done, the modems become
transparent to the user, and GPIB/RS232 commands can be entered as if the power meter is
connected directly to the remote computer.
The power meter can also be configured to automatically dial a specified number if one or
more predetermined error conditions are met.
When an instrument state change occurs that initiates an AUTODIAL sequence, the power
meter will send an escape sequence "+++" to the modem. It will then output commands to
determine if there is a modem connected and, if there is, whether it is connected through to
another modem. If a modem is found and it is not connected to a remote modem, the power
meter will dial the number specified in the "phone number" field. When the connection to the
remote computer is established, the power meter will send the serial SRQ message.
When an autodial sequence is initiated, different sets of characters will be seen on the remote
PC depending on what is connected to the power meter serial port.
Note
It is recommended that there is only one serial command in each command string.
Terminate each command with a newline character.
Note
Serial interface remote operation is not available when the ML243xA Series Power
Meter is operating from the internal battery.
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