Circuit to display contents of eprom?

[neazoi]

Circuit to display contents of eprom or PIC memory?

Is there such a circuit that will be able to display the contents of an eprom or PIC memory in hex or bin etc in an array of 7 segment displays? Have you ever seen such a circuit?

I think some old expensive programmers had this feature and they were also able to program the flash without using a computer.

 

[betwixt]

For an EPROM, all you need is some switches and pull down resistors connected to the address pins and two binary to 7-segment decoders on the data pins.
PIC memory is a bit more complicated but you can read it using the "read" command in programming mode - unless the code protection is turned on. You can read about the method if you look at Microchip's web site for details on programming specifications, the method is different for each type of PIC.

Brian.

 

[neazoi]

For an EPROM, all you need is some switches and pull down resistors connected to the address pins and two binary to 7-segment decoders on the data pins.
PIC memory is a bit more complicated but you can read it using the "read" command in programming mode - unless the code protection is turned on. You can read about the method if you look at Microchip's web site for details on programming specifications, the method is different for each type of PIC.

Brian.

Something like this?
hagi-online: BinDisplay_EPROM

By the way have you found any eprom or PIC programmer that does not need a PC to be programmed? something like an LCD to enter code (hex probably) and some kind of keyboard. This is a little bit weird, I have not seen this.

 

[KerimF]

At work, when I like that my assistants do the programming of the product MCUs, I give them a copier from a serial EEPROM (like 24C512) to MCU. So I just give them one SEEP (serial memory) that includes the program/data and they need to press a button to program each MCU. Naturally this can be made to program EPROM as well but I didn't need it.

Added:
In the far past, in the 70's, my first programmer I designed and built was for the early versions of PROM and EPROM (I think they needed 3 supplies for programming). These memories were for the codes of my Z80 CPU projects. The main entries were 8 switches and a push button to enter a byte in a RAM memory. The display was essentially formed by 8x8 LEDs that shows the last 8 bytes. Naturally I added keys for moving the reading/writing address. I am not sure now how I displayed the address; by 7-segment display or by a row of LEDs. Then when all data is checked; one by one, the RAM content was transferred to the EPROM in one continuous session (only later one-byte programming became possible). Writing a program (in machine code since I didn't have an assembler) then programming it into an EPROM to get a workable controller took me one to two months. A similar program now will likely take me a couple of hours

 

[doraemon]

Hello!

Is there such a circuit that will be able to display the contents
of an eprom or PIC memory in hex or bin etc in an array of 7 segment
displays? Have you ever seen such a circuit?

Better than seen one: I made one just last week. (See attachment).
Well, it's not a 7-segement because I like freedom of graphic displays,
but beside this it does not only show the contents but also edits it.

For an EPROM, all you need is some switches and pull down resistors
connected to the address pins and two binary to 7-segment decoders
on the data pins.

You are talking about a parallel EEPROM. This cannot work with serial
EEPROMs.


Dora.

 

[neazoi]

A schematic on this project would be very helpful.

I did not know it is so easy to display the contents of an eprom. Eproms like 2764 or 27128 do not support byte programming right? They have to be programmed all at once, so the contents of the program must be stored in some kind of memory and then be programmed on the eprom at once.

Another interesting aspect would be an embedded assembler, where you could enter assembly on an LCD and the embedded assembler could translate it to HEX and program a chip

 

[doraemon]

Hello!

This one cannot program a 2764 or 27128, so a schematic would not be very useful.
As for the schematic of this one, there are exactly 2 connections: SDA and SCL of the EEPROM,
so I don't think it's absolutely necessary to bother drawing schematics.
The rest of it is a development board, so you can use any development board.

Now writing an assembler for such a small device is not really a good idea. It's quite complicated
to write a good assembler, and on top of that there are many free assemblers around for each
processor.

I made this because in one of my projects, the configuration of a device is stored in a serial
EEPROM, so I can quickly edit the configuration on site without a PC. Serial EEPROMS support
byte programming.

By the way, you don't need to translate assembly code to hex to program it. You need to
translate it to hex only for display purposes. In the code I wrote, I display lines of 4 bytes.
I translate them first to hex in order to edit them, and then recombine them to bytes for
programming.

Dora.

 

[betwixt]

KerimF - I still have some old 2708 EPROMs that need positive and negatve supplies and I think it was 21.5V for programming, thank goodness electronics has advanced !

Neazoi - I think some EPROMS can be byte programmed but the more modern flash types certainly have to be block erased and reprogrammed in one operation. They need an 'unlocking' sequence of byte commands sent to them so just using switches isn't really practical.

PICs, provided they are not code protected, can be read serially by using their PGC and PGD pins. You have to apply the programming voltage on the -MCLR pin then clock the 'read' command and the address in to the PGD pin. Of course, doing this requires some automated hardware, trying to do it by hand would be almost impossible.

Brian.