Specifications

Operating Manual SEFRAM 4451
M4451 A00
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Setting the device to address 31 puts it in the 'off-bus' state. In this state it will not respond to
messages on the GPIB. If the device is in the REMS when set to address 31, an internal 'return-
to-local' command will be given, setting the device to the LOCS. If the device is in the RWLS,
the 'return-to-local' command is ignored, and the device remains in the RWLS.
The only way to then re-establish communication with the device over the GPIB is to cycle the
power, and to then change the address to that required from the front panel.
4.5 MESSAGE EXCHANGE PROTOCOL
The device decodes messages using the Message Exchange Protocol (MEP) defined in IEEE
488.2. The following functions implemented in the MEP must be considered.
4.5.1 The Input Buffer
The device has a 128-byte long cyclic input buffer. Decoding of remote messages is begun as
soon as the input buffer is not empty, that is, as soon as the controller has sent at least one byte
to the device. Should the input buffer be filled up by the controller faster than the device can
remove the bytes and decode them, the bus handshake is not completed until room has been
made for more bytes in the buffer. This prevents a fast controller from overrunning the device
with data.
If the user has sent part of a Program Message, but not the Program Message Terminator, and
he wishes to abort the message decoding and execution, the Device Clear command may be
sent, or front panel operation resumed (in REMS only).
4.5.2 The Output Queue
The device has a 100-byte long output queue in which it stores response messages for the
controller to read. If at the time a response message is formatted and the queue contains
previously formatted response messages, such that there is not enough place in the queue for the
new message, the device will put off putting the message in the queue until there is place for it.
The Status Byte MAV bit indicates when set that part or all of a response message is ready to be
read.
4.5.3 Response Messages
The device sends a Response Message in response to a valid query. All queries return a single
Response Message Unit, and all query responses are generated at the time the query is parsed.
4.5.4 Coupled Commands
Coupled Commands are either commands whose execution validity depends on the value of
other parameters, or commands whose execution changes the value of another parameter. The
execution of commands designated as being coupled is deferred until all other commands in the
same Program Message have been executed. The coupled commands are then grouped together
according to their functionality, and executed as a group. All parameters of the SEFRAM 4451
are coupled.
4.6 INSTRUMENT IDENTIFICATION
The *IDN? common query is used to read the instrument's identification string. The string
returned has the following format:
SEFRAM 4451,0,V1.0
4.7 INSTRUMENT RESET
The *RST common command effects an instrument reset to the factory default power up state.
4.8 SELF TEST
The *TST common query causes the device to perform a self-test. This self-test consists of
checking the status of the pulse generator's period, pulse and output cards.
4.9 COMMAND SYNTAX