Do 1 kilobit EPROMs exist? I only need 32 bytes, but I know that EPROM memory is usually measured in kilobits so I am assuming that the smallest is at least 128 bytes. If they don't exist, what alternatives are there? Like I said, I only need 32 bytes.

 

24LC00 is 16bytes then 24LC01 is 128 bytes. That's the smallest I know of in the uCHIP world anyway. They're dirt cheap. I don't think a 32 byte one exists. The die wouldn't be that much smaller and at that level, it's the package that costs the money.
EDIT: EPROM or EEPROM?
http://www.microchip.com/wwwproducts/en/AT24C01D 128 bytes, .09 in qty 1 for the AT24C01D-SSHM-B SOIC package.

Use the extra memory for redundant records, checksums, feature creep etc.

 

Do 1 kilobit EPROMs exist? I only need 32 bytes

They exist, but before 16Kb, they used multiple power supplies.

EDIT: First was 2Kb, the 1702

Do you really want EPROMs, or just nonvolatile memory? Do you want parallel or serial output? EPROMs come in 0.6" wide packages.

 

You could use a 2732 and ground the unneeded address lines

 

Do 1 kilobit EPROMs exist? I only need 32 bytes, but I know that EPROM memory is usually measured in kilobits so I am assuming that the smallest is at least 128 bytes. If they don't exist, what alternatives are there? Like I said, I only need 32 bytes.

That they are usually measured in kbits does not mean that the smallest is 1 kb. There are smaller. But today most of the small stuff is obsolete.

Maxim makes 256 bit (32 byte) EEPROMs. But I don't know of any of these small EEPROMs that aren't serial interfaces. Will that work for you?

In looking at DigiKey's site, the smallest parallel I/O EEPROMs they have in stock are 64 kbit.

 

24LC00 is 16bytes then 24LC01 is 128 bytes. That's the smallest I know of in the uCHIP world anyway. They're dirt cheap. I don't think a 32 byte one exists. The die wouldn't be that much smaller and at that level, it's the package that costs the money.
EDIT: EPROM or EEPROM?
http://www.microchip.com/wwwproducts/en/AT24C01D 128 bytes, .09 in qty 1 for the AT24C01D-SSHM-B SOIC package.

Use the extra memory for redundant records, checksums, feature creep etc.

I did mean EPROM, because I'd like to be able to reuse it if possible and I have an EPROM eraser. Unless EEPROMs can be written to AND erased with an EPROM programmer? I don't think so, but I don't know.

Maxim makes 256 bit (32 byte) EEPROMs. But I don't know of any of these small EEPROMs that aren't serial interfaces. Will that work for you?

Not without extra hardware, unfortunately.

I have tons of diodes and need to buy tons of transistors anyway. What if I just use diodes or transistors to make an old fashioned ROM? Since I only need 256 bits (32 bytes), and not all of those bits will be 1, I think this might be the most frugal route, at least. But is it practical?

 

Unless EEPROMs can be written to AND erased with an EPROM programmer?

EEPROMs can be written to by EPROM programmers. Depending on the part number, they have the advantage of being able to erase and rewrite a byte at a time. As you already know, EPROMs have to be completely erased before they can be programmed and only have an endurance of about 100 program/erase cycles. EEPROMs are spec'ed for 1000-100k cycles.

Don't think any EEPROMs of less than 16KB were manufactured and the largest were around 64KB or 256KB.

Another option might be NVRAM. I use X2210A (64x4 bits) when I need a small amount of nonvolatile, rewritable memory.

 

I did mean EPROM, because I'd like to be able to reuse it if possible and I have an EPROM eraser. Unless EEPROMs can be written to AND erased with an EPROM programmer? I don't think so, but I don't know.

Depends on the EPROM programmer and the EEPROM specifics.

Not without extra hardware, unfortunately.

I have tons of diodes and need to buy tons of transistors anyway. What if I just use diodes or transistors to make an old fashioned ROM? Since I only need 256 bits (32 bytes), and not all of those bits will be 1, I think this might be the most frugal route, at least. But is it practical?

This is rather contradictory. The amount of extra hardware that you would need to add to your circuit to interface to a serial EEPROM is tiny compared to the circuitry you would need to add in order to implement a 256 bit ROM.

You could just use a small 8-bit micro to create the interface.

But if you are just doing a one-off project and not something that's in any kind of volume production, just use the smallest parallel EEPROM you can find. You're only talking about a couple of dollars.

 

Don't think any EEPROMs of less than 16KB were manufactured and the largest were around 64KB or 256KB.

DigiKey has, in stock, EEPROMs ranging from 128 bit (Microchip 24LC00 serial EEPROM for under 25 cents) and the largest are 32 Gb (Toshiba TH58NVG5S0FTA20 parallel EEPROM for $32.58).

Another option might be NVRAM. I use X2210A (64x4 bits) when I need a small amount of nonvolatile, rewritable memory.

DigiKey doesn't stock that -- their range of NVSRAMs (that are in stock and available in single units) is quite limited ranging from 64 kb to 1 Mb with costs in the $8 to $25 range.

Where do you source the X2210A from? Who makes that part? I haven't been too successful tracking it down.

 

DigiKey has, in stock, EEPROMs ranging from 128 bit (Microchip 24LC00 serial EEPROM for under 25 cents) and the largest are 32 Gb (Toshiba TH58NVG5S0FTA20 parallel EEPROM for $32.58).

I meant to say parallel EEPROMs like the original 2816. The 32Gb part must be FLASH that they're incorrectly referring to as EEPROM. EEPROM allow individual bytes to be programmed.

Where do you source the X2210A from? Who makes that part? I haven't been too successful tracking it down.

It's a Xicor part. Only available from places catering to old parts. I bought a bunch from someone liquidating company inventory.[/QUOTE]

 

@Green Bean Maybe if we knew what the actual application was we could give you some more directed advice - surely something better than diodes and transistors. We're pretty good at that, as a group.

 

Depends on the EPROM programmer and the EEPROM specifics.



This is rather contradictory. The amount of extra hardware that you would need to add to your circuit to interface to a serial EEPROM is tiny compared to the circuitry you would need to add in order to implement a 256 bit ROM.

You could just use a small 8-bit micro to create the interface.

But if you are just doing a one-off project and not something that's in any kind of volume production, just use the smallest parallel EEPROM you can find. You're only talking about a couple of dollars.

Well yes, the extra hardware is more complicated, but I wouldn't have to spend anymore money. But you are right it would probably be more practical to just use the smallest EEPROM I can find. I guess that's what I should do.

@Green Bean Maybe if we knew what the actual application was we could give you some more directed advice - surely something better than diodes and transistors. We're pretty good at that, as a group.

Yes, I'm sorry, I'm sorry! I'm trying to make a table of Hamming weights. So you put in a 5 bit number on the address lines and get the Hamming weight on the data line. I don't need an 8 bit data line, but I couldn't find any EPROMs smaller. But like I said, I think I'll just use an EEPROM.

 

No worries. What you describe is a good application for some sort of byte-wide memory if you are using discrete logic. If that's the case, then takao's suggestion fits a good as any. If the Hamming table is part of some processor-based affair just read the EE into RAM and use it from there.
Good luck!

 

Well yes, the extra hardware is more complicated, but I wouldn't have to spend anymore money. But you are right it would probably be more practical to just use the smallest EEPROM I can find. I guess that's what I should do.


Yes, I'm sorry, I'm sorry! I'm trying to make a table of Hamming weights. So you put in a 5 bit number on the address lines and get the Hamming weight on the data line. I don't need an 8 bit data line, but I couldn't find any EPROMs smaller. But like I said, I think I'll just use an EEPROM.

What is going to be using these weights? If there is any kind of a processor (such as a microcontroller, DSP, FPGA, or other programmable logic) involved then you almost certainly have the room in the device configuration to store your lookup table.

 

You could use a 2732 and ground the unneeded address lines

Probably not easy to find EPROM nowadays - everyone's using FLASH, and I think there's weird things about sequencing CE, R/W and OE or something.

A voice at the back of my head says a DIL-8 EEPROM and a serial to parallel interface might be less traumatic.

 

Probably not easy to find EPROM nowadays - everyone's using FLASH, and I think there's weird things about sequencing CE, R/W and OE or something.

A voice at the back of my head says a DIL-8 EEPROM and a serial to parallel interface might be less traumatic.

I don't know how less traumatic that will be. It sounds like his application needs a RAM -- he puts in a five bit value and want to get a three bit output. The five bit values occur randomly.

 

Yes, I'm sorry, I'm sorry! I'm trying to make a table of Hamming weights. So you put in a 5 bit number on the address lines and get the Hamming weight on the data line. I don't need an 8 bit data line, but I couldn't find any EPROMs smaller. But like I said, I think I'll just use an EEPROM.

Another options is to use a PLD (programmable logic device). If you can program EEPROMs, then you should be able to program PLDs.

 

What is going to be using these weights? If there is any kind of a processor (such as a microcontroller, DSP, FPGA, or other programmable logic) involved then you almost certainly have the room in the device configuration to store your lookup table.

I'm thinking about designing a circuit to play Conway's Game of Life. The Hamming weight of the surrounding 8 cells (represented with 8 bits) determines the new state of the cell in the center (with some help from additional logic). But it doesn't use a microprocessor.