Hi everyone!
I've been working a homebrew computer project for a while and I've run into a problem when I try to write to memory.
The problem is just how to manage setting the write and chip select pins at the approiate time. What I need is for the chip select pin to be low(IE do not allow any reads or writes) until the write pin goes high(initiating a write) then I need the chip select pin to wait a little amount of time to allow the address pins to settle then, have the chip select pin go high. I also need the chip select pin to go low before the write pin goes low.
I attempted to do this with a 555 timer in monostable mode. I connected the trigger pin of the 555 timer to the write pin so that when the write pin was put high, the 555 timer would delay the chip select pin for a little while and also turn it low after a determined amount of time. There are a few problems with this method. First I need an edge detector which I have had trouble implementing. Second, there still exists a point where two signals must arrive is a certain order.
So I wondering if anyone has a better way to do this. To be perfectly clear what it is I'm trying to do, here a little diagram:
I would like to keep this as simple as possible because of limited breadboard space. Also, I don't want to use anything like microcontrolers and such. I'd like to just use simple logic.
Any input appreciated.
I've been working a homebrew computer project for a while and I've run into a problem when I try to write to memory.
The problem is just how to manage setting the write and chip select pins at the approiate time. What I need is for the chip select pin to be low(IE do not allow any reads or writes) until the write pin goes high(initiating a write) then I need the chip select pin to wait a little amount of time to allow the address pins to settle then, have the chip select pin go high. I also need the chip select pin to go low before the write pin goes low.
I attempted to do this with a 555 timer in monostable mode. I connected the trigger pin of the 555 timer to the write pin so that when the write pin was put high, the 555 timer would delay the chip select pin for a little while and also turn it low after a determined amount of time. There are a few problems with this method. First I need an edge detector which I have had trouble implementing. Second, there still exists a point where two signals must arrive is a certain order.
So I wondering if anyone has a better way to do this. To be perfectly clear what it is I'm trying to do, here a little diagram:
I would like to keep this as simple as possible because of limited breadboard space. Also, I don't want to use anything like microcontrolers and such. I'd like to just use simple logic.
Any input appreciated.