Keithley 2520, User Manual, Page: 178 / 329

Model 2520 User’s Manual Status Structure 11-19
Programming example - program and read register set
The command sequence in Table 11-8 programs and reads the measurement register set.
Registers are read using the binary format (which directly indicates which bits are set).
The command to select format (FORMat:SREGister) is documented in
Table 11-2 .
Queues
The Model 2520 uses two queues, which are first-in, first-out (FIFO) registers:
• Output Queue — Used to hold reading and response messages.
• Error Queue — Used to hold error and status messages. (See Appendix B .)
The Model 2520 status model ( Figure 11-1 ) shows how the two queues are structured with
the other registers.
Output queue
The output queue holds data that pertains to the normal operation of the instrument. For
example, when a query command is sent, the response message is placed in the Output
Queue.
When data is placed in the Output Queue, the Message Available (MAV) bit in the Status
Byte Register sets. A data message is cleared from the Output Queue when it is read. The
Output Queue is considered cleared when it is empty. An empty Output Queue clears the
MAV bit in the Status Byte Register.
A message is read from the Output Queue by addressing the Model 2520 to talk after the
appropriate query is sent.
Table 11-8
Program and read register programming example
Command Description
FORM:SREG BIN
STAT:MEAS:ENAB 512
STAT:MEAS:COND?
STAT:MEAS? Select binary format to read registers.
Enable BFL (buffer full).
Read Measurement Condition Register.
Read Measurement Event Register.