On Thu, 11 Feb 1999 20:21:36 +0200 Zack Cilliers writes: >I want to interface DRAM to a pic. I have two questions. >1. To refresh the DRAM can i only address the columns >and the rows will be addressed automatically? Accessing a row will refresh all the columns in that row. To refresh the whole chip, you need to access all the rows within the rated maximum time (usually 4 to 16 ms). DRAMS larger than 256 Kbit and some 256K ones have a mode called "CAS-before-RAS refresh". This mode uses a single pulse to refresh a row. The row address to be refreshed comes from an internal counter dedicated to this purpose, so it is not necessary to supply an anddress to the chip. This mode is usually the best approach to refreshing if you can't set it up so that regular data access will also satisfy the refresh requirement. >2. To read the DRAM must i first latch the column addresses > or the row addresses. First latch the row address using RAS, then the column address using CAS. DRAM's aren't hard to use, but it essential to obtain and carefully study a manufacturer's data sheet. ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]