The Wait Loop is what happens when your calculator is sitting on your desk and wondering what you’ll need next. This article covers that.
The calculator is ON. The PRGM-RUN switch is in RUN. It’s waiting for you to press a key. This is the microcode sequence for that:
HP25 Logging started. ; A= 0000ffffffffff B= 21000000000000 M1=20000000000202 ; S= ...3.5.......... WaitLoop: 00742 0 -> s 3 00743 if 0 = s 3 then goto 01672 00745 if 0 = s 15 then goto 00742 WaitLoop: 00742 ...
s3 is the RUN-PRGM switch. It is checking to see if we’ve decided to program the calculator instead. We haven’t. We’re still in RUN mode. s3 is 1.
s15 is key_pressed. If a key hasn’t been pressed, it goes back to the start of the loop.
It keeps wondering.
It’s pretty straight forward.
By the way, you can also see ” 0.00″ in the display; given what is in the A and B register. B=2 blanks out the first digit (” “). B=1 lights up the decimal point after the second one (“0.”). B=0 after that shows the remaining digits. For the woodstock calculators (HP-21 to HP-29 and HP-67), an “f” in the A register shows as blank.
This is part of the HP-25 topic.
