HP-46 calculator (was Re: Britain is Great (Back from the Island))

Mike Ford <mikeford(a)socal.rr.com> wrote: It made it act somewhat like the 55's stopwatch; the 65 didn't have one. The stopwatch was apparently intended to be a feature of the 45 early on in the development, but was later cancelled. The code was left in the ROM, and was activated by STO followed by the switch under the right half of the ENTER key. The ENTER key is molded to only press the switch under its left half, so this feature was probably intended to be inaccessible on unmodified calculators. However, by the nature of a scanned key matrix, it is possible to get a "phantom key" by pressing three other keys. In this case, it can be done by pressing CHS, 7, and 8 simultaneously. It is difficult to make this work consistently without a lot of work, so many people used the "penny trick", placing a penny on those three keys to help press them simultaneously. Other people added a shim to the ENTER key so that it would press the right-hand switch. Since the stopwatch was not a supported feature of the 45, they manufactured it using the same LC oscillator circuit of most of the other calculators, so it isn't very accurate. Many people installed a crystal, and at some point HP actually published an application note on doing this, although they didn't support it, and it voided the warranty. Yes. There's an IFDEF that makes the ENTER key generate the right-hand keycode instead of the normal left-hand. Eric