I have a circuit using a DS89C450 micro and an external 1m(128kx8)ROM. I am using P1.0 as an upper address bit which is low for this test. I have /CE tied low and use /OE derived from p3.7(/rd) to read from the ROM. When I do a movx a,@dptr /OE does go low and about 10ns later the data becomes valid but goes away after 30ns. Shouldn't the data be valid throughout the entire /OE ? When I send the data I received to the serial port, it was 00h and not what I saw for the 30ns but what was after the 30ns. I have msg'd the manufacturers tech support also. Any ideas?
- posted
17 years ago