Hi,
In one of my project i connected 8031, 27c256 and 8255.Here the A15 line is given common to Chip enable of EPROM and also connected to G1-pin of address decoder via a NAND gate.
So if the A15 is low eprom is selcted and if high 82c55 is selected.
But now i want to use 64kb eprom. I cannot connect the A15 like above.
Can anybody suggest how to do the accessing?
exactly the same way as before because normally the eprom lives in code space and the pio in XDATA space. HINT: the EPROM should be accessed via PSEN the PIO via /RD and /WR.
BTW: all of your devices are obsolete.
Thomas
Now the problem comes in the selection of chip.
Bcos previously i used the A15 to select the EPROM and the 8255 using my program.
Now the A15 is used and i cannot access 8255.
"previously i used the A15 to select the EPROM and the 8255 using my program. Now the A15 is used and i cannot access 8255"
Did you read the Hint from Thomas Zepf?
Do you have anything else mapped into XDATA space?
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