6264 static RAM

The 6264 is an 8kB static RAM, available in 70 to 200 nanosecond access time variants. It can function on both the NES PPU's 8080 style bus (separate /WE and /OE strobes) or on the CPU's 6500 style bus (by grounding /OE and connecting the R/W signal to /WE). The 62256 is similar but has 32kB of RAM instead.

6264 Pinout (62256 in parentheses)

The 6264 has been used for work RAM and save RAM in numerous NES games, commonly decoded at $6000-$7FFF. The 62256 is used in RacerMate Challenge II, Romance of the Three Kingdoms II, and a few Famicom games.

• 6264: 8Kx8-bit SRAM
• 62256: 32Kx8-bit SRAM

           .----\/----.
(A14) nc - |01      28| - +5V
     A12 - |02      27| - /WE
      A7 - |03      26| - CS2 (A13) 
      A6 - |04      25| - A8      
      A5 - |05      24| - A9      
      A4 - |06      23| - A11       
      A3 - |07      22| - /OE       
      A2 - |08      21| - A10       
      A1 - |09      20| - /CS1    
      A0 - |10      19| - D7      
      D0 - |11      18| - D6      
      D1 - |12      17| - D5      
      D2 - |13      16| - D4      
     GND - |14      15| - D3      
           `----------'

621024 Pinout (62512 in parentheses)

In the NES, these chips might be used in "EPROM emulators", or devices into which a game is loaded from an external source (such as a connected personal computer or a NAND flash) before it runs.

• 621024: 128Kx8-bit SRAM
• 62512: 512Kx8-bit SRAM (breaks name pattern)

           .----\/----.
(A18) nc - |01      32| - +5V
     A16 - |02      31| - A15
     A14 - |03      30| - CS2 (A17)
     A12 - |04      29| - /WE
      A7 - |05      28| - A13
      A6 - |06      27| - A8      
      A5 - |07      26| - A9      
      A4 - |08      25| - A11       
      A3 - |09      24| - /OE       
      A2 - |10      23| - A10       
      A1 - |11      22| - /CS1    
      A0 - |12      21| - D7      
      D0 - |13      20| - D6      
      D1 - |14      19| - D5      
      D2 - |15      18| - D4      
     GND - |16      17| - D3      
           `----------'

Signal descriptions

A0-A12(-A14)

address

D0-D7

data

/CS1 and (when present) CS2 (chip selects 1 and 2)

when /CS1 is low and CS2 is high, the chip is selected and will accept input or provide output to the data bus.

/WE (write enable)

When the chip is selected, if this pin is low, the eight-bit data D will be written to the address inside the RAM specified by A

/OE (output enable)

When the chip is selected, if this pin is low and /WE is high, the eight bit data in the RAM at address A will be output onto the pins D.

The difference between /OE and the chip selects is that the 6264 responds much faster to /OE, but it draws less power when the chip selects are deasserted.

A circuit to generate /CS1 for decoding a 6264 RAM at $6000-$7FFF is described at PRG RAM circuit. It can also be used to decode a 62256 if you have latches available to control A13 and A14.