As you said in your previous mail, we hook up the following lines:

68k address: 23 68k control: 5 DRAM address: 9 DRAM control: 4 TOTAL: 41

If we do not connect up the 8 data lines, how do we make them high impedance when not doing a read/write operation? Also, for the refresh, am I correct in saying that as long as we generate a CAS before RAS every 15us, without specifying the exact word line, the refresh will work?

Shezad Okhai

-- Shezad Okhai (shezad.okhai@utoronto.ca), January 29, 1999

Answers

If the /OE on the DRAM chips is off (high) then they will not drive, so just make sure that your default state has /OE high.

With a CAS-before-RAS refresh (not other types of refresh) you don't need to supply an external address. The DRAM chips have an internal counter that gets incremented every time a CAS-before-RAS cycle happens, so as long as you do this kind of refresh once every 15us everything will work.

Robin

-- Robin Grindley (grindley@eecg.toronto.edu), January 30, 1999.