On Thu, 12 Mar 1998 05:30:38 +0000 Danjel McGougan writes: >Now to the problem. I need to use DRAM which I have very little >experience in using (I'm really a software guy, not hardware). How >does one proceed to design a battery backed-up system with a DRAM and >a PIC processor? I understand that the DRAM must go into self-refresh >mode when the power is cut. Also, how do I get the memory to refresh >during normal operation? I understand that I probably need some kind >of external counter and perhaps something else to run the refreshing. You really need to RTFM on the RAM chip you intend to use, since there are several different kinds. At the very least, it'll support CAS-before-RAS refreshing. This means you can keep the data in the DRAM alive just by holding all the pins except RAS and maybe WE low, and hae your PIC or an external timer apply periodic (about 30 KHz) short low pulses to RAS. The DRAM chip contains an internal counter that will sequence through all the rows for you. Maybe "self-refresh" involves an internal timer as well, I'm not familiar with that. When power is on, you can do CAS-before-RAS cycles periodically, interspersed with your data reading or writing cycles if the machine is active. _____________________________________________________________________ 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 Or call Juno at (800) 654-JUNO [654-5866]