|A little clarification about power modes|
Message #10 Posted by Andrés C. Rodríguez (Argentina) on 10 Aug 2002, 6:12 p.m.,
in response to message #9 by Ed Martin
The HP 41C/CV has 3 power modes:
1-RUN: While executing a program or a function (for instance, for less than a second when you press [SIN], or all the time needed to finish a program since you pressed [R/S]). In this mode, the calculator draws the most power (peripheral operation like Wand or Card reading may take even more power). It is supposed that the calculator spends not a large perecentage of time in RUN mode.
2-STANDBY or IDLE: The calculator is doing "nothing", except detecting eventual keyboard activity. The display keeps showing the last contents it had. This mode uses little power, and is key to the long battery duration, since the calculator seems to be active when it is really doing very little.
As the CPU is not running while IDLE, the display, which is the only component "working" in that moment, is the only place in which a timer could be counting. After 10 minutes in such mode, the display intends to shut off the calculator by means of the DPWO signal (Display PoWer Off).
Any RUN mode activity (i.e.: keypresses) resets the timer.
If the calculator has Flag 44 on (continuous mode on), it will ignore the display timeout, but in normal cases it will shut off.
So, after executing ON, the calculator may remain for a long time in IDLE mode, even without any RUN mode event.
[[Note: I am not sure if ON prevents the timer to generate the DPWO signal; or if flag 44 causes the CPU software to ignore DPWO, which seems more probable. A nice challenge for hardware experimenters...]]
3-SLEEP. In SLEEP mode the calculator appears to be off, it is just feeding a little current from the batteries to the RAM chips in order to keep their contents. Apart from detecting activity on the ON key, nothing is being done, and the power consumption is very low.
[[A sleeping calculator may be turned on by some peripheral activity like Wand or Card reading, or by the Time module]]