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.
Certain Konami VRC boards take a 24-pin 2Kx8 SRAM:
,---\/---.
A7 --| 1 24|-- Vcc
A6 --| 2 23|-- A8
A5 --| 3 22|-- A9
A4 --| 4 21|o- /WE
A3 --| 5 20|o- /OE
A2 --| 6 19|-- A10
A1 --| 7 18|o- /CS1
A0 --| 8 17|-- D7
D0 --| 9 16|-- D6
D1 --|10 15|-- D5
D2 --|11 14|-- D4
Vss --|12 13|-- D3
`--------
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.
.----\/----.
(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
`----------'
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.
.----\/----.
(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
`----------'
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.
Categories: Integrated circuits