Friday, 12 August 2011

8. SRAM Working.

I managed to get the SRAM chip working. I only have a limited number of pins on the Arduino and I needed 4 just to control the chip. I decided to use 3 pins for the address lines and 3 more pins for the data lines. All other pins on the chip I connected to ground effectively making them low or 0. With this configuration I can read/write the values 0 to 7 to the memory addresses 0 to 7 because 7 is the biggest value you can make with 3 binary digits 111 = 1x4 + 1x2 + 1x1 = 7.

There are 17 address lines on this SRAM chip I'm using labelled A0 through to A16 and that allows 217 memory addresses which is 131072 or 128K. In today's world this is an insignificant amount of RAM, but to put it into perspective, the Sinclair ZX80 had 1K of RAM and a 4K ROM, the ZX81 had 1K RAM and an 8K ROM, the Spectrum had 48K of RAM and a 16K ROM.

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