problem writing to static ram 62256

Thread Starter

dmowziz

Joined Jan 18, 2019
76
Someone please come to my rescue. I'm trying to write data into the ram but after writing in 3 addresses, when I go back to check the adresses, the values change

What can be the problem?

Thanks
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
Actually no. I'll post circuit of what I'm doing when I'm done so I can get advice

I believe I'm doing it right. OE and CE are both low. Then WE is connected to V with a pullup through a button (When I press the button WE goes low to write into the chip)

Can you make guesses as to what can be wrong so I check please
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
here is "schematic"..I hope you understand (first time using eagle or similar). If i add more wires it will look messy
 

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Thread Starter

dmowziz

Joined Jan 18, 2019
76
hi dm,
Sorry, I don't use Eagle, unable to open the file.
E
zzzzzzzzzzzzzzzzz..

Actually it seems to be working now, maybe not

I'm writing the values with a dip switch. Do the values of pull up resistor matter in this case? I'm using 18k

btw, what do you use?
 

MrChips

Joined Oct 2, 2009
22,068
I never use DIP switches nor 18k pull up with SRAM because the SRAM would be controlled by an MCU.
What are you trying to accomplish?
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
I never use DIP switches nor 18k pull up with SRAM because the SRAM would be controlled by an MCU.
What are you trying to accomplish?
look who's here..hehehe
I used arduino to write to the chip at first but it doesn't work well

I am trying to write data into the chip for an 8 bit cpu.

How would you do it?
 

OBW0549

Joined Mar 2, 2015
3,566
I believe I'm doing it right.
You aren't.

Operating a 62256-type static RAM is pretty simple.

Read sequence:
  1. Start with /WE, /OE and /CE high (NOTE: all three control signals are active-low), and data pins un-driven
  2. Apply desired address to address lines
  3. Bring /CE low
  4. Bring /OE low
  5. Read data from data pins
  6. Bring /CE and /OE high
  7. Address may now change for next read or write operation
Write sequence:
  1. Start with /WE, /OE and /CE high and data pins un-driven
  2. Apply desired address to address lines
  3. Apply desired data to data lines
  4. Bring /CE low
  5. Bring /WE low
  6. Bring /WE high
  7. Bring /CE high
  8. Address may now change for next read or write operation
  9. New data may now be applied to the data lines for next write operation, or drive removed for read operation
There are various timing requirements in those sequences and there are a few possible variations. Consult the data sheet for specific timing requirements.
 

LesJones

Joined Jan 8, 2017
2,726
Your schematic is incomplete. I would expect to see how you are feeding data into the I/O pins for a write and how you are displaying the data for reading it. You don't show how you are de-bouncing the button to generate the write pulse. You don't show how you are driving the 8 low order address lines.
Here is your schematic exported as a .PNG file. (So that people that do not use Eagle can view it.)
220219.png
To do this. Click on file, select export as image, give it a file name with a .PMG extension.

Les.
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
Your schematic is incomplete. I would expect to see how you are feeding data into the I/O pins for a write and how you are displaying the data for reading it. You don't show how you are de-bouncing the button to generate the write pulse. You don't show how you are driving the 8 low order address lines.
Here is your schematic exported as a .PNG file. (So that people that do not use Eagle can view it.)a
View attachment 170754
To do this. Click on file, select export as image, give it a file name with a .PMG extension.

Les.
Yes It's incomplete..feeding data into the I/O pins made it look messy and I wanted people to understand. The lower 8 address lines to dip switch. I/O pins to other dip switch

I am trying what the arrogant sir (OBW0549) said - always arrogant!, seems to be working so far. Yet to read from chip
 

ericgibbs

Joined Jan 29, 2010
11,091
Moderation:
If you want the learned people on this site to give their time in trying to help you with a technical problem, it would be polite to show them respect.

So please stop behaving in a disrespectful way or no one will be willing to help you.

E
 

MrChips

Joined Oct 2, 2009
22,068
Being disrespectful to people, such as your teachers, who are trying to help you through life is just a stupid and infantile thing to do.

When are you going to grow up?
 
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