CASIO fx-5200P Scientific Computer teardown

[jebem]

... and reassemble to fully working order.

I bought this machine from a private seller that enjoys Casio pocket computers.
This one was not working, so I got it for a few Euros.
Opening, dismantling, cleaning and readjusting battery contacts was enough to bring it back to life.

Despite the had life this specimen had, all the keys work flawlessly. This is a Casio know how. They designed these machines to last forever. I know the keys do not have mechanical feedback like in most HP models but it gets the job done.

This looks like another Casio scientific calculator but it is programmable in BASIC language as used in other Casio pocket computers of the same era (mid 80's)..

It has a limited RAM memory size of just 1KByte but it can be expanded with an additional 1KByte by inserting a RAM Expansion Pack in the back.




After inserting two new CR-2032 button cell batteries, a hardware reset is mandatory to initialize the system correctly.




On a machine without additional RAM Expansion Pack installed, typing DEFM and pressing EXE returns the default RAM memory partitioning after a hardware reset is:
- 26 variables
- 544 program steps


The RAM memory partitioning can be modified as required using the command DEFM.
Each program step takes one Byte of RAM.
Each variable takes 8 program steps consuming 8 Byte.

The above default partitioning results in a total of ((26 * 8) + 544) = 752 Byte.
Therefore the internal 1KByte RAM memory have (1024 - 752) = 272 Byte that are not available for the end user.
These 272 Byte would be equivalent to 34 internal variables (registers).

The RAM Expansion Pack would add up to 1024 program steps or 128 variables, depending of the user needs.

Going into programming mode (WRT / Mode 1), it shows 544 remaining program steps after a hardware reset.




The LCD display showing all annunciators




Power supply information in the back cover: 6VDC, 0.01Watt.
This translates to an average current consumption of 1.7mA.



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