6264 RAM IC

[foTONICS]

Hey all, my teacher gave us this problem of needing a 16k x 8 bit memory. He gave us an example of one 6264 and how to set it up but now he wants us to add a second one so that we can get the required 16k. I know how all the enable, read/write functions work and also how the data inputs are arranged (74LS244) feeding into D0-D7 but as far as addressing goes...

I have the first IC addresses full A0-A12, and have the second IC's first address A0 (mimicking A13), is this correct? I have the other 11 addressing inputs of the second IC grounded. Am i supposed to be running any connections (aside from the chip enable/read/write functions) from the first IC over to the second IC?

I did some researching of the data sheets but it just mentions the basic read/write requirements and chip enable functions

 

[Laplace]

Reading the datasheet suggests these RAM chips were intended to be connected in parallel for expansion, ie, A0->A0....A12->A12, I/On->I/On, CE1->CE1, WE->WE, OE->OE. But the CE2 line will multiplex the RAM chips. See if you can make that work.

 

[(*steve*)]

Well, the difference between 8k and 16k is just one bit.

If only there was a way to use that bit to enable just one of the chips at a time.

 

[foTONICS]

Reading the datasheet suggests these RAM chips were intended to be connected in parallel for expansion, ie, A0->A0....A12->A12, I/On->I/On, CE1->CE1, WE->WE, OE->OE. But the CE2 line will multiplex the RAM chips. See if you can make that work.

ya you were right. Today I asked him about it and he showed me having both chip enables tied together to a switch but having one inverter going to only one of the IC's. This worked as turning the switch HIGH enabled one IC and turning it LOW enabled the other. Also the parallel A0->A0 etc, etc, was correct too

thanks guys!

 

[Harald Kapp]

In a real application you wouldn't want a switch to select one out of two RAMs. think about steve's comment - the missing bit is there right in front of your eyes (or should I say on the processor's pins?).

Harald