Hi Steve,

I am using the DS1221 RAM decoder chip to select them. A15 goes to pin 4(A) and use an inverting buffer scheme on PSEN to select the low ram chip at pin 14(CE) of the DS1221. Ram (CE) pins are put to pins 13 and 12 of the DS1221. That is working fine as I stated when running BASIC-31 normally. Using the DS1221 chip also gives me the option of memory backup during power failure. So I am thinking of storing the program in RAM but it still worries me. I would like to use a more permanent methode such as the eprom "cold start". Does this help you with my problem?