Key Combinations The DM calculators have some special key combinations, some are the same as on the HP calculators, some are unique to DM calculators.

Buttons Function Description
DM1x DM41
Press & Hold     Press & Release Press & Hold     Press & Release
[A] + [ON] [A] + [ON] display time/date display time/date for 5 minutes
[B] + [ON] N/A benchmark evaluate benchmark compared with orig. calc
[C] + [ON] [C] + [ON] serial console switch to serial console (see below)
[E] + [ON] [E] + [ON] show information firmware version & battery voltage
[CHS] + [ON] [CHS] + [ON] LCD settings change LCD contrast with buttons [+], [-], [3], [Σ+]
[STO] + [ON] [STO] + [ON] daylight saving adjust RTC decrement -1h
[RCL] + [ON] [RCL] + [ON] daylight saving adjust RTC increment +1h
[7] + [ON] N/A change font cycle through available fonts
[9] + [ON] [8] + [ON] change speed toggle between 12MHz and 48MHz
[/] + [ON] [9] + [ON] key test same as on the original calculator
[⨯] + [ON] N/A self test same as on the original calculator
[-] + [ON] N/A power reset same as on the original calculator
[+] + [ON] N/A endless test same as on the original calculator
[.] + [ON] N/A toggle . and , same as on the original calculator
new in V23:
[SST] + [ON] [x<>y] + [ON] start time/date adjustment use [/], [⨯], [-], [+] to change and [ENTER] to set

Serial Console
  • set calculator in serial console mode by [C]+[ON]
  • connect miniUSB cable to computer. drivers for many platforms including Win, MacOSX, Linux can be found here
  • open terminal program; on windows putty (or hyperterm if you are brave enough), minicom under linux, use Terminal under MacOSX
  • for Linux/MacOSX find the device using "ls /dev/ttyUSB*" or "ls /dev/tty.S*" if you installed silab driver
  • set terminal program to 38400,8n1 (no flow control) (for example on Linux use "minicom /dev/tty.SLAB_USBtoUART 38400,8n1" or on MacOSX "screen /dev/tty.SLAB_USBtoUART 38400,8n1")
  • en- and decode utility (html with jscript) for RAM save and restore function
  • a great HP-15C Simulator for Windows, Linux and Mac OS Xsupports data exchange with the DM15
  • instructions for the serial console for Mac and Windows (PDF)
Battery replacement
  • turn calculator off; the content remains for about 30 seconds without battery
  • unscrew all four screws
  • remove calculator from case
  • replace battery
  • put it back together, don't tighten the screws too much
Change LCD contrast
  • [CHS]+[ON] starts the LCD mode setting
  • use [+], [-], [SUM+] and [3] to change the contrast
Change font The models DM11, DM12, DM15 and DM16 include three font types: slim, bold and block
The combination [7]+[ON] cycles through all three font types