Keithley 2651A Reference Manual page 193

Section 3: Functions and features
To write-protect specific digital I/O lines to prevent their values from being changed:
1. Press the MENU key, then select DIGOUT, and then press the ENTER key or the navigation
wheel
2. Select WRITE-PROTECT, and then press the ENTER key or the navigation wheel
3. Set the decimal value as required to write-protect digital I/O lines within the range of 0 to 16,383
(see Digital I/O bit weighting
wheel
4. Press the EXIT (LOCAL) key as needed to return to the main menu.
5. To remove write protection, repeat the above steps, but enter the original value in step 3.
3-86
Model 2651A High Power System SourceMeter® Instrument Reference Manual
.
(on page 3-87)), and then press the ENTER key or the navigation
.
.
2651A-901-01 Rev. A / March 2011