HP -28S Quick Reference
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HP-28S
System Operations
Contrast
adjustment
• Press and hold ON
• Press + or – to change the contrast
• Release ON
Clear memory
• Press and hold ON
• Press and and release INS and → (cursor right)
• Release ON
WARNING: This clears the entire memory including stack, variables,
programs and flags. This is essentially a "restore to defaults".
Endless-loop
interruption
• Press and hold ON
• Press and release ↑ (cursor up)
• Release ON
This will clear the stack, go to HOME, clear UNDO, COMMAND, LAST,
clear the CUSTOM menu, deselect TRACE printing.
Note that a program or other lengthy operations can usually be
interrupted by pressing "ON".
System test
• Press and hold ON
• Press and release ↓ (cursor down) or ← (cursor left)
• Release ON
This will execute a system test once (↓) or repeatedly (←).
Press ON/↑ to abort the test. The single test will also execute the
keyboard test.
Note that the system test behaves differently with different software
versions.
Keyboard test
• Press and hold ON
• Press and NEXT
• Release ON
This will execute a keyboard test where the user must press all keys
from top left to bottom right.
Note that the system test behaves differently with different software
versions.
SYSEVAL Execute subroutine at absolute address. For debug only.
Warning: Addresses change between different versions of the HP-28S
software. Calling an invalid address usually resets the machine and
causes a "Memory lost" error.
• #10d SYSEVAL return the software version number
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