wpm
Member level 2
eprom 27256
I have made a circuit with a 27256 Eprom in Proteus 6.3 & SP1.
Eprom settings: Vpp to +5V, /OE and /CE both to GND, didn't change the Advanced Propeties.
The image file is a BIN file, start address is 0x000 and when I use Debug the memory contents is OK.
The address lines A0..A2 are connected to a counter 74LS90 with a clock of 3.6kHz. The address lines A8..A14 to GND. The address lines A3..A7 connected by a switches so I can put a +5V or GND signal to the input.
The lines A0..A2 are used to move the contents of the Eprom one step further. Using the counter the Eprom output lines D0..D7 don't change by every signal on A0..A2 but stay in one position.
When I disconnect the address lines A0..A2 from the counter and connect them by switches either to +5V or GND the output lines D0..D7 change corresponding to the memory contents.
Why does the circuit don't work with the counter?
I have made a circuit with a 27256 Eprom in Proteus 6.3 & SP1.
Eprom settings: Vpp to +5V, /OE and /CE both to GND, didn't change the Advanced Propeties.
The image file is a BIN file, start address is 0x000 and when I use Debug the memory contents is OK.
The address lines A0..A2 are connected to a counter 74LS90 with a clock of 3.6kHz. The address lines A8..A14 to GND. The address lines A3..A7 connected by a switches so I can put a +5V or GND signal to the input.
The lines A0..A2 are used to move the contents of the Eprom one step further. Using the counter the Eprom output lines D0..D7 don't change by every signal on A0..A2 but stay in one position.
When I disconnect the address lines A0..A2 from the counter and connect them by switches either to +5V or GND the output lines D0..D7 change corresponding to the memory contents.
Why does the circuit don't work with the counter?