HP 42S: Difference between revisions

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649 bytes added ,  11:59, 3 February 2022
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(Memory layout WIP)
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<nowiki>*</nowiki>note: the top row of keys are customarily labeled A-F from left to right.
<nowiki>*</nowiki>note: the top row of keys are customarily labeled A-F from left to right.


HP 42s has two resets: Master reset which puts the calculator back to "factory condition", clearing all memory with On+A+F and Machine reset with On+C which interrupts any program, clears certain flags and sets the calculator into a state ready to receive user input again.  
HP 42s has two resets: Master reset which puts the calculator back to "factory condition", clearing all memory with On+A+F and Machine reset with On+C which interrupts any program and sets the calculator into a set state ready to receive user input again, but does not cause any memory loss.  


As with the HP 27S and HP 17B, the self test is triggered with On+D.
As with the HP 27S and HP 17B, the self test is triggered with On+D.
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Due to having its ROM dumped and emulators developed (and many exploration prior) the memory layout of the HP-42s is generally well know:
Due to having its ROM dumped and emulators developed (and many exploration prior) the memory layout of the HP-42s is generally well know:
{| class="wikitable"
{| class="wikitable"
|+
|+Memory Layout of HP-42s
(left inclusive right exclusive)
!Address Start (hex)
!Address Start (hex)
!Address End (hex)
!Address End (hex)
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|-
|-
|00000
|00000
|1FFFF
|20000
|ROM
|ROM
|
|Executing from 00000 is the only way to exit the debugger without using a reset.
Executing from 023F1 (default entry point for debugger) displays the software revision and a one byte warm-start log. (often erroneously reported along with revision, e.g. A7, C5.....)
|-
|-
|40000
|40000
|4020C
|4020C
|Display
|Display
|Column 0, 66, 1, 67 ........ 64, 130, 65 with 4 nybbles per column for 16 pixels, 131 columns in total.  
|Column 0, 66, 1, 67 ........ 64, 130, 65 with 4 nybbles per column for 16 pixels per column, 131 columns in total.  
|-
|-
|
|40210
|
|4024D
|
|Annunciators
|
|Each word contains five nybbles that is either 00000 (off) or FFFFF (on).
40210-40215 is a word that lights up all announciator.
 
from 40218 to 4024D each word controls multirow, shift, printing, busy, battery low, G and RAD (together forming GRAD) annunciators respectively.
|}
|}
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