Need help. EEPROM

Thread Starter

royashley99

Joined Nov 20, 2021
31
I am wanting to make the circuit from Ben Eaters video
and i can only get my hands on the 28C64-15 and not the 28c16, would i be able to use it in the same way and just not use the extra pins
 

sagor

Joined Mar 10, 2019
536
The 28C16 seems to be available on sites like Ebay or Amazon, though how good they are is another question. You need to be able to program the chip as well...
 

sagor

Joined Mar 10, 2019
536
You can use the larger chip if designing something where you can access the pins directly, like breadboarding. Tie the unused address pins (high addresses) to either low or high and just use the bottom 16k bits.
Both chips seem to have 150ns access time, so timing should be the same.
 

Ian0

Joined Aug 7, 2020
4,119
I am wanting to make the circuit from Ben Eaters video
and i can only get my hands on the 28C64-15 and not the 28c16, would i be able to use it in the same way and just not use the extra pins
Yes.
Tie the spare address inputs low. Otherwise, your other inputs will be selecting data at the top end of the memory, not the section starting at address zero.
 

Papabravo

Joined Feb 24, 2006
17,580
does it matter if i tie the unused pins to high or low?
If you know where to put your data it does not matter. The 28C64 has four times the data space as the 28C16. If you tie the unused address lines low you will use the 2K (bytes) block that goes from 0x0000 to 0x07FF in the larger device. If you tie them both high then your data will be in the 2K block from 0x1800 to 0x1FFF.

There are, of course, two other methods you could choose for what to do with those two unused address lines for a total of four possible blocks ot 2K worth of data, or you could write the identical data into each 2K block and then it would not matter what you did as long as you don't let them float.
 

dl324

Joined Mar 30, 2015
13,836
And is there a EEPROM that i can replace it with
They are both EEPROMs. IIRC, 16K is the smallest they made. Some manufacturers had a 256K part; maybe larger.

does it matter if i tie the unused pins to high or low?
The unused pins must be tied HIGH or LOW. Since you only need 256 addresses, you can choose where to put them. You can use the first 256 addresses, the last, or any other "block" of 256 addresses.
 

Thread Starter

royashley99

Joined Nov 20, 2021
31
Yes.
Tie the spare address inputs low. Otherwise, your other inputs will be selecting data at the top end of the memory, not the section starting at address zero.
are there any easier to get alternatives for the 28c16 eeprom that i can program and use in the exact same way
 

Papabravo

Joined Feb 24, 2006
17,580
are there any easier to get alternatives for the 28c16 eeprom that i can program and use in the exact same way
Probably not. The reason you can't get them is economics. They made a certain number and when those were gone and replaced by parts with more memory for the same price it was no longer good business. IMHO you are SOL.
 

dl324

Joined Mar 30, 2015
13,836
are there any easier to get alternatives for the 28c16 eeprom that i can program and use in the exact same way
Nothing is going to be easier to use than a 16 bit wide EPROM. Jameco.com has 27C210 and 27C1024 in stock.

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If you don't have access to a UV eraser, don't make a programming mistake.

They also have 28C16 in stock.
 
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