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VX4101A Operational Modes
2–4
VX4101A MultiPaq Instrument User Manual
Asynchronous Protocol allows asynchronous query and command of instru-
ments. When you enable the Asynchronous Mode, the VX4101A stores
responses in a queue. When you request data from this queue via a VXI read,
you receive responses in first-in, first-out (FIFO) order, regardless of which
instrument produced the response. Since these responses can be returned in a
different order than the queries, the VX4101A uses a different method of
associating a response with the associated query. This is described in a later
section entitled Response Formats.
The Asynchronous Protocol ensures that the response queue never blocks the
parser, as follows:
1. One entry in the queue is reserved for the overflow message.
2. If the queue becomes full, any subsequent writes to the queue will result in a
loss of the message.
If a message has been lost in this fashion, then the next VXIbus read will
result in transmission of the error message in the buffer overflow. Data
which is already in the response queue will remain there until it is read.
The 488.2 synchronization commands, *WAI, *OPC, and *OPC? are handled as
global synchronization devices by the Asynchronous Protocol. This allows you
to explicitly control the order of commands to multiple instruments on a single
device.
NOTE. Although it is possible to switch back and forth between strict 488.2
enforcement and the Asynchronous Protocol during instrument operation,
Tektronix recommends that you choose one mode or the other and leave the
instrument in that mode until it is reset. Switching back and forth during
operation could cause the instrument to enter an undesirable state under some
circumstances.
This section lists and describes the SCPI command set used in the Asynchronous
Protocol. The command structure is as follows:
SYSTem:LANGuage [[SYNChronous] | ASYNchronous]
This command allows you to choose between strict 488.2 protocol enforcement
and the Asynchronous Mode. The default state of this feature will be SYNChro-
nous, which implies strict 488.2 enforcement. An argument of ASYNchronous
enables the Asynchronous Mode. Both query and command are supported.
Asynchronous Mode
Commands