Section 3 Operation
3-18
3-70. Calibration and Test Functions. Codes 20
through 39 are used in calibration, testing and trouble-
shooting of the Model 1121A. These functions can be
disabled using Option switch A4S1-4 to prevent acci-
dental use resulting possible loss of current calibration
and memory data.
3-71. S/N Delay Functions. Codes 40 through 49
provide user configurable delay between the signal
measurement and noise measurement. The delay allows
time for a device under test to respond to the change in
output level during the signal-to-noise measurement
cycle.
3-72. Frequency Sweep Resolution Functions. Codes
50 through 59 allow selection of linear or logarithmic
frequency sweep modes and logarithmic sweep
resolution. The default mode after initialization is code 55.
3-73. Sweep Rate Functions. Codes 60 through 69
allow selection of the delay for each sweep step. The
delay is based on the number of consecutive analyzer
measurements before a data point is plotted. The default
mode after initialization is code 63.
3-74. AC Detector Selection Functions. Codes 70
and 71 are used as an alternate mode for selection of the
AC detector type. The default mode after initialization is
the rms detector, code 70.
3-75. Source Impedance Selection Functions. Codes
75 through 77 are used for selection of the source output
impedance. The default mode after initialization is 600
ohms, code 77.
3-76. dBV/dBm Display Mode Functions. Codes 80
through 86 are used to select the reference used to
calculate the logarithmic display value. All logarithmic
levels will be displayed in the form selected. The default
mode after initialization is code 80, dBV.
3-77. Option Switch, A4S1, Operation. Several of the
Model 1121A operating features are internally program-
mable by setting bit switch A4S1. Gaining access to the
switch requires that the cover be removed. The option
switch consists of eight separate switches which change
the operating conditions of the Model 1121A. Some of the
option switch functions can be altered using the special
functions 1 through 8. Table 3-8 list the individual switch-
es and their function.
3-78. Positions 1 and 2 of A4S1 are used for
end-of-string (EOS) control for the IEEE-488 bus.
End-or-Identify (EOI) is always recognized and asserted
in addition to the EOS characters selected. Position 3
determines the pen-up active state of the PEN output on
the rear panel. Position 4 is available to restrict the use of
special functions 20 through 39. These special functions
are associated with calibration and repair of the
instrument. Position 5 determines the operation of the
IEEE-488 SRQ function. When enabled the SRQ line will
be set true if the SRQ key is depressed or if the
instrument is in the remote condition and an error is
generated. Position 6 determines the auto-recall function.
Normally the REC key must be depressed in order to
recall any program location. When enabled the
auto-recall function automatically performs the REC
function when using the step keys to increment or
decrement the PRGM function. However, entering a
program location directly using the DATA ENTRY keypad
requires that the REC key be depressed to execute the
recall function. Positions 7 and 8 are used for test modes.
When the lamp test is selected the display LEDs, display
legends, and key LEDs with the exception of the LEVEL
and SOURCE function keys will be constantly illuminated.
The remaining function keys will be illuminated in
sequence.
3-79. Error Codes. Error codes and descriptions for
the Model 1121A are listed in Table 3-9. The error codes
will appear in the SOURCE display window and will be
returned by the talk-status (TS) IEEE-488 bus function if
executed. The SRQ status byte will consist of the error
code expressed in excess sixty-four. The status code 64
decimal means the SRQ was activated by the front panel
SRQ key rather than an error.
3-80. REMOTE OPERATION.
3-81. Any front-panel operation of the instrument with the
exception of the LINE ON/OFF switch can be remotely
controlled under direction of an IEEE-488 interface
controller.
3-82. Setting the Bus Address. To set the IEEE-488 bus
address (MLTA), depress the ADRS key, enter the
address number by means of the DATA ENTRY keypad
and use the ENTER key to complete the entry. The ad-
dress may be any decimal number from 0 to 30, inclusive.
A secondary address is not implemented.
3-83. Entering the Remote Mode. The instrument is put
in the remote mode by addressing it as a listener with
remote enable (REN) true. In the remote state the
keyboard is disabled, except for the LCL/INIT key and the
POWER ON/OFF switch, and the REM status an-
nunciator is illuminated.
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