CASIO fx-5200P Scientific Computer

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 to be useful as a pocket computer 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 1024 program steps or 128 variables depending of the user needs.

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

The LCD display showing all annunciators:

Power supply: 6VDC, 0.01Watt.
Average current consumption of 1.7mA

Machine teardown.

The two zebra connectors and the common ground spring coil interconnects the alpha keyboard to the main machine body.

 

Lifting the main PCA reveals the keyboard assembly.
The LCD display is glued to the front cover and needs to be slightly heated to be removed without damaging the LCD unit.

Back aluminum cover and power switch among other parts.

The three flex connectors from the alpha keyboard.

The keyboard membranes have embbeded hard plastic keys.
 

PCB back side.

PCB top side (main component side).
- Hitachi HD61747B16 - SoC processor (CPU, LCD & KB driver, ROM)
- Hitachi HD61914C- 1KByte static RAM

This fx-5200P uses the same chip set as found on other Casio machines, only differing on the ROM firmware. For instance:

- fx-4000P
SoC processor: Hitachi HD61747B38
Memory: HD61914 8kbit static RAM

- FC-200
SoC processor: HD61747B55
Memory: HD61914 1KByte static RAM.

General parts view.