Alright, I have decoded A15 A14 A13 to single 8 bit addr by 74138 ( 3 to 8 decoders).
My PROM is of 8Kbytes and RAM is also same ( 2864 & 6264) the PROM is set at 0000H to 1FFFH by chip enable of Yo of 74138 chip and RAM at 4000H to 5FFFH from Y2 of 74138 chip to chip select of memory IC....
The problem is that,i don't understand why other pin of 74138 decoder are working, mean only Y0 and Y2 should give output as i am using only these addr 0000H to 1FFFH by chip enable of Yo of 74138 chip and RAM at 4000H to 5FFFH...
please clear my doubt, by putting some light of your experience...
My PROM is of 8Kbytes and RAM is also same ( 2864 & 6264) the PROM is set at 0000H to 1FFFH by chip enable of Yo of 74138 chip and RAM at 4000H to 5FFFH from Y2 of 74138 chip to chip select of memory IC....
The problem is that,i don't understand why other pin of 74138 decoder are working, mean only Y0 and Y2 should give output as i am using only these addr 0000H to 1FFFH by chip enable of Yo of 74138 chip and RAM at 4000H to 5FFFH...
please clear my doubt, by putting some light of your experience...