Operation Modes of RPN-65 Pro
- Loading a Plus card will automatically set the calculator to Plus mode - Leaving Plus mode with Plus card inserted will eject the card - Convert Plus cards to standard cards(or vice versa) by duplicating the card - If not in Plus mode, underflow will halt a running program. Tap R/S to continue. |
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111 Additional Registers
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In addition to the HP-65's regular 9 registers, you may use R0, registers A..E and a..e, and registers 00 through 99. Full store and recall register arithmetic is supported. Extended registers may be accessed just like regular registers by prepending their address with a decimal point. Examples:
Registers may be printed out by the PRINT REG command (f⁻¹ REG) in modes UI and Plus. Extended registers 00..99 are only printed when the paper tape printer mode is set to TRACE. Extended registers 00..99 may be cleared by the command f CLx. Registers A..e get cleared by the command f REG, along with the regular registers. Note that f CLx may not be programmed by simply tapping the two keys in W/PRGM mode, as this would clear the program memory. Instead, enter the two keycodes – 31 and 44 – directly into the program listing in RUN mode. Alternatively, you may type the command name CLXT or CLEXT. Another solution is to enter this key sequence (in W/PRGM mode): f EEX CLx g BST DEL |
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Unlimited Register Arithmetic
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RPN-65 Pro removes the HP-65's limitations on register arithmetic functions. Register arithmetic supports both STO and RCL operations and works with any register (0..9, A...E, a..e, 00..99). Examples:
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105 Additional Labels
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With 105 labels in addition to those built into HP-65, you'll probably never run out of labels again. Available labels are: A..E, a..e, 0..9, 00..99. Every label may the target of a subroutine call by using the GSB command (f⁻¹ GTO). To address a 2-digit label, insert a "+" after the command, followed by the 2-digit label number. Examples:
The location (or locations, if used more than once) of each label is listed, followed by the number of unused labels. With extended labels 00..99 (Plus mode), only the first occurrence in the program is shown. Unused extended labels are not listed. Note There is a subtle difference between using A and GSB A to call subroutine A. While the former searches for the first occurrence of LBL A beginning at the top of memory, the latter searches from the next program step. This applies to all labels A..E and a..e. |
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Additional Flag Commands
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RPN-65 adds handy toggle and test commands to the flag operations. All commands are invoked by the prefix key DSP.
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HP-65 Peculiarities
Back in 1974, the HP-65 was the first magnetic-card-programmable handheld calculator. Due to technical limitations, some characteristics seem rather odd in today's view.
They did not appear in later calculator versions. As an example, notice that deleting step 100 of a program also deletes step 99.
It would make sense, for example, to assume that "one keypress = one program step". However, many 2-step instructions were merged into a single step,
for example g NOP, g LSTx, STO/RCL 1 to 8 (but not 9!).
In particular, the LBL function and the label name occupied two steps, which could lead to remarkable side-effects, especially when single-stepping and
switching between RUN and W/PRGM modes.
A glaring deficiency was the absence of a back-step key.
Single-stepping (SST) one or more steps too far by accident was best remedied by deleting and reinserting steps.
Note that RPN-65 supports back-stepping in UI and Plus modes (press g SST).
If operated in vintage mode, RPN-65 faithfully simulates a number of these oddities. For example:
- Sticky Minus Sign
Set the display to 0.00 (CLx)
Press the CHS key. The display shows -0.00.
Press the CHS repeatedly. The display never changes back to 0.00. - Cued Stops
It is sometimes helpful to put a familiar number into the X register before stopping for data. If a cue number is created as a program step immediately preceding R/S, it is not lifted into the stack and the number is overwritten by the data you key in.
For the following demonstrations, load the default programs by setting RPN-65's mode to "Enhancements Off" or "Fast", then flipping the power switch OFF, then ON.
Delete the LBL E subroutine (steps 20 to 23), then recreate LBL E at steps 97 to 100 as follows: LBL E CHS RTN
(Hint: Use GTO.96 in UI mode – or GTO.096 in Plus mode – to quickly access step 96, enter the code, then return to mode "Off" or "Fast".)
001: 23 LBL
002: 11 A
003: 35 g
004: 04 1/x
005: 24 RTN
006: 23 LBL
007: 01 B
008: 32 f
009: 09 √x
010: 24 RTN
...
097: 23 LBL
098: 15 E
099: 42 CHS
100: 24 RTN
- Cocked RTN
This refers to the fact that a RTN instruction not preceded by a call to the corresponding label is treated as NOP.
Example 1:
– Tap 5 A. The result is 0.20, as expected.
– Now enter 5 GTO A R/S. You'll get 0.45 (=√0.20) because the RTN in step 005 executes as NOP.
Example 2:
– Address step 002 (by executing RTN W/PRGM SST RUN)
– Tap 5, then SST
This will execute the subroutine A, found at step 001. The calculator dutifully executes the code (steps 003..006),
then returns to the step following the call, which is 003.
Since we're single-stepping, the program stops here to show 0.20. Tap SST twice to execute the remaining steps 003 and 004.
The final result is 5.00.
Example 3:
– Clear the program memory (W/PRGM f PRGM).
– Still in programming mode enter LBL A 1 + RTN. Return to RUN mode.
– Clear the stack (f STK).
– Tap A. The result is 1.00, as expected.
– Clear the stack again, then tap RTN, then R/S (or GTO A R/S).
– You'll get 2.00. The program ignores the RTN, then executes the 95 default NOPs to arrive at the top of memory, finally stopping
at the RTN in step 5.
More operations to try out and explore:(RUN = switch to run mode, W/PRGM = switch to program mode)
(If you tried Example 3, restore the original sample program shown above first.)
EXECUTE | DISPLAY | COMMENTS
____________________|_____________________________|_______________________________________
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RUN 5 GTO E | 5.00 W/PRGM 15- | Addresses step 99
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[Common start] | |
1. RUN SST | -5.00 W/PRGM 42- | CHS
2. RUN SST | -5.00 W/PRGM - 24- | RTN
3. RUN SST | -5.00 W/PRGM 00 00- | At top of memory
[Continuation 1]
4. RUN SST SST | -5.00 W/PRGM 11- | Executes LBL, A (no action)
5. RUN SST SST | -0.20 W/PRGM 04- | Executes g,4 (= g 1/x)
6. RUN SST | 4.00 W/PRGM 24- | RTN
[Continuation 2]
4. RUN SST SST SST | -5.00 W/PRGM 35- | Executes LBL, A, g (no action)
5. RUN SST | 4. W/PRGM 04- | Executes 4 (g-shift cleared)
6. RUN SST | 4.00 W/PRGM 24- | RTN
[Continuation 3]
4. RUN SST | -5.00 W/PRGM 23- | LBL (executes as NOP)
5. RUN SST | -0.20 W/PRGM 11- | Executes A (entire LBL A subroutine)
6. RUN SST | -0.20 W/PRGM 35- | g (step 03)
7. RUN SST | 4. W/PRGM 04- | Number key 4 (g-shift cleared)
8. RUN SST | 4.00 W/PRGM 24- | RTN