On Wed, 1 Jul 1998 15:14:41 -0700 WF AUTOMACAO writes: >Hi, :( > > I don't believe what's happening with a program that i try to >execute a program in 2 >external EEPROM connected in a PIC17C756 (MICROPROCESSOR MODE) What is your PIC clock rate? It is quite possible that the PIC is running too fast for the EEPROMs to supply the proper program instructions to it. The timing diagrams in the back of the PIC data say that the time between when the PIC outputs a valid address and the memory must provide the correct data is 3 xtal cycles - 30 ns. At 25 MHz, that is only 90 ns. The delay through the address latch must also be accounted for, maybe 20 ns. So the memory must have an access time of 70 ns or less. Parallel EEPROMs are rather slow to read compared to RAM or EPROM. Newer Microchip 28C64s are spec'd at 150 ns. Other ones may be 200 or even 450 ns. None of these chips will work with the PIC going 25 MHz, or even 16 MHz. Not allowing enough access time can cause the chips to read wrong, though often consistent, data. This would explain one program working and another not. For a test, slow the PIC way down and see if the programs operate properly. With a 4 MHz crystal, the memories have about 700 ns to respond, which should be plenty. _____________________________________________________________________ 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]