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Making a Casio RA-500 RAM card by modifying the Casio RC100 ROM card
The RC100 ROM card is not greatly different in physical structure than the RA-500 RAM card. It should be possible to modify the ROM card by replacing the ROM chip with an SRAM chip that is in the RAM card, and a few extra components. Here is some initial info. Note that the RAM chip pin outs are slightly different to the ROM chip pin outs and will need to be rerouted with wires to correct. |
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Click on the pictures to view zoomed in |
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RA-500 opened |
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RA-500 schematic |
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RA-500 Parts list |
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Casio RA-500 RAM card |
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Casio RC100 ROM card (for comparison) |
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Links for parts to make the RAM card
The 256k SRAM memory chip, surface mount: http://au.element14.com/bsi-brilliance-semiconductor/bs62lv256scg70/sram-32kx8-3-5v-comm-70ns-28sop/dp/1816345 The 74HC27 NOR logic chip, surface mount: http://au.mouser.com/ProductDetail/Texas-Instruments/SN74HC27DR/?qs=AgY10sKTvDK%2fBz6A3pjt%252bJHnBo4WCZnkl%252bwvwjHokrQ%3d The DAN212k diode, surface mount: http://au.mouser.com/ProductDetail/ROHM-Semiconductor/DAN212KT146/?qs=4kLU8WoGk0ubGcRyLz63vNLfL%2fGrIh99o6EDKhLPqr0%3d Other things: Maybe a couple of surface mount resistors if needed: 10k resistor: http://au.mouser.com/ProductDetail/Bourns/CR0201-JW-103GLF/?qs=URDPQ%2fj0cz1ThTIPL9aNWT79Px%2fJ4oi3 100k resistor: http://au.mouser.com/ProductDetail/Bourns/CR0201-JW-104GLF/?qs=URDPQ%2fj0cz0Ia2IBB3Qkj0LLlRSEt0xb 220pF capacitor: http://au.mouser.com/ProductDetail/AVX/W3F11A2218AT1F/?qs=IytdewgIZqJlcjsiMZ2CN5v9n6%252bBXNdL |
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Discussion about making the RAM card can be read at the EZ-VZ chat page:
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SRAM chip datasheet |