Design Ideas: April 27, 1995

The PAL-based dual-port RAM in Fig 1 replaces more expensive circuits based on the Intel 8207-8 programmable memory controller. Fig 1 shows a 32-kbyte, dual-port memory. A data-acquisition system can write to the memory through one port, while a computer reads the memory.

The memory has separate data and address buses for the outside system and the host computer. The PAL provides control signals, such as read/write (R/W), output enable (OE), and chip select (CE) for both sides. The Listing is the fuse map for the PAL. The compressed ZIPfile attached to EDN BBS /DI_SIG #1667 contains a copy of the fuse map of the PAL in ASCII. You could easily expand the system to incorporate more memory. (DI #1667)