Bit 5 - Standard Event Status Bit (ESB) Summary
Message. The ESB summary message is an IEEE-
488.2 defined message. Its state indicates whether
or not one or more of the enabled ESB events have
occurred since the last reading or clearing of the
Standard Event Status Register.
Bit 6 - Master Summary Status (MSS)/Request
Service (RQS) Bit. Its state indicate if the device
has at least one condition to request service. The
MSS bit is not part of the IEEE-488.1 status byte
and will not be sent in response to a serial poll.
The RQS bit, however, if set, will be sent in response
to a serial poll.
Bit 7 - Not used.
4-14-1. Reading the Status Byte Register
The Status Byte Register can be read with either a
serial poll or the *STB? common query. Both of
these methods read the IEEE-488.1 STB message.
The value sent for the bit 6 position is, however,
dependent upon the method used.
4-14-1-1. Reading with a Serial Poll
When serial polled, the generator returns the 7-bit
status byte plus the single bit RQS message. The
status bye and RQS message are returned to the
controller as a single data byte. The RQS message
is sent on line D107 (bit 6). RQS TRUE means that
bit 6 line is asserted (pulled to a low voltage) when
the status byte is sent. The response represents the
sum of the binary-weighted values of the Status Byte
Register.
Reading the Status Byte Register with a serial
poll sets the RQS message FALSE until a new
reason for service has occurred. The STB portion
of the Status Byte Register is read non-destructively.
The value of the status byte is not altered by a
serial poll. Once the model 8020 has generated an
RQS, its status byte should be read to clear the
SRQ line so the controller can detect an SRQ from
another device. Otherwise the instrument will con-
tinuously assert the SRQ line.
4-14-1-2. Reading with the *STB?
The *STB? common query causes the generator to
send the contents of the Status Byte Register and
the MSS (Master Summary Status) summary message
as a single <NR1 Numeric Response Message>
element. The response represents the sum of the
binary-weighted values of the Status Byte Register.
The *STB? common query does not alter the status
byte.
4-14-1-3. Clearing the Status Byte Register
The entire Status Byte Register can be cleared by
removing the reasons for service from the Auxiliary
Status Registers. Sending the *CLS common com-
mand to the device after a <Program Message
Terminator> and before <Query Message Unit> ele-
ments clears the Standard Event Status Register
and clears the output queue of any unread messages.
With the output queue empty, the MAV summary
message is set to FALSE.
Methods of clearing the other auxiliary status
registers are discussed in the following. The RQS
message in the Status Byte Register will be FALSE.
The use of the IEEE-488.1 DCL or SDC commands
another method of clearing the Status Byte Register,
however, in some cases it is not recommended to
use this method since the entire front panel set-up
is reset to factory default values.
4-14-1-4. Service Request Enable Register
The Service Request Enabling Register is an 8-bit
register that enables corresponding summary mes-
sages in the Status Byte Register. Thus, the appli-
cation programmer can select reasons for the model
8020 to issue a service request by altering the
contents of the Service Request Enable Register.
Command Response Format (*)
FRQ? FRQ 1.000E+3(terminator)
AMP? AMP 1.00E+0(terminator)
OFS? OFS 0.00E+0(terminator)
WID? WID 10.00E-3(terminator)
CAR? CAR 100E+0(terminator)
STP? STP 9.000E+3(terminator)
SWT? SWT 1.00E+0(terminator)
MRK? MRK 5.000E+0(terminator)
DCO? DCO 0.00E+0(terminator)
RPT? RPT 1.00E+0(terminator)
(*) NL END is normal terminator. Ter-
minator may change (see paragraph
4-12-4).
Table 4-7. Response Message Format Summary
Model 8020 IEEE-488.2 Operation
Page 4-23
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