G850VS update

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Richard
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Inscription : 01 févr. 2015 12:10

G850VS update

Message par Richard » 11 mars 2015 15:20

Hi guys !

I now have a Japanese user manual that I'm slowly converting to English. I'm making a compilation of my notes including confirmed lists of basic and C commands, functions of keystrokes, how to enter C programs, machine code etc. I'll release a draft copy it here when I get some free time...

I have also disassembled another G850VS, photo's available soon. I have found though that the G850VS is VERY similar to the G850V (the memory chip has changed etc) and contains the following...

1. Additional battery terminals labeled BTY2+ and BTY2-. It appears they are for a backup battery (that used to sit beneath the 'name' label on the rear of the calculator). Components linked to these pads are missing though.

2. Buzzer terminals !!, labeled BZ+ and BZ-, difficult to see but a capacitor and diode may be missing. Testing to follow.

3. A Sharp S1L50752F25N2 gate array that connects to the side 'system bus' connector, probably housing a copy of the Z80 processor and other functions. At the side of this is a three-pin oscillator 'X1' (ceramic ?) and printed on top is 800C743 (could be 800G743).

4. A 70 nano seconds access time flash memory chip faster and much larger than expected (4Mbit organised as 512k 8-bit bytes in eight 64k sectors). Part number EN29F040A-70TCP.

5. Three epoxy covered surface mounted chips. two are clearly connected to the display, the third sits next to the flash memory chip ?.

Some chips are 5v, others are 3v. There are many test points, the only ones to note are three labeled BNK5 BNK6 BNK7 which I guess are some kind of memory bank switching (as Z80 processors historically had a very limited address bus).

Regards...

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