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serial to Ram

M

Marty

Veteran Member
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Jul 26, 2009
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Location
Boulder , Colorado USA
Hi All;
I am looking for an article by Steve Ciarcia (SP?) that took Data from the serial port and converted it to Paralell and then put it in Ram , which Via a switch the Ram was either seen by the serial port or when in the other mode , it would look like an eprom, to what ever project you are hooked to.. I have No problem with the Eprom to Ram part, But I am not sure about the serial to Pararell part and how to get the downloaded program to start at location 0000 in the Ram... I seem to have lost the Article...
THANK YOU Marty
 
Hi All;
I don't know, I would need to find a copy and have a look see. It looks like the Eprom section, would help some.. I'll see IF I can get a copy..
THANK YOU Marty
 
Just curious: what's it for?

Most of the ones out there these days use uCs, FPGAs, etc.

A parallel interface is usually much easier; depending on your situation a battery-backed RAM chip might even be an answer.
 
Hi Mike;
Thanks for asking .. As some of you know I have an 8085 SpaceByte S-100 CPU card, and when I programmed the 2716 eprom for it, the Serial port Does not show its signon message.. So I have modified the Board to accept Ram IC's and I I could either find this Circuit or build something like it.. I Could put small program in Ram/Eprom and run them and find out IF there is a Bad IC on the Board or a bad connection or IF I have Bad Code.. But, I don't want to go thru the process of programming another Eprom every time I need or want to make a code change... I had the article before and even built it and then after not needing it for a long time I unwrapped it and used the sockets for someting else.
THANK YOU Marty
 
Marty said:
Hi Mike;
Thanks for asking .. As some of you know I have an 8085 SpaceByte S-100 CPU card, and when I programmed the 2716 eprom for it, the Serial port Does not show its signon message.. So I have modified the Board to accept Ram IC's and I I could either find this Circuit or build something like it.. I Could put small program in Ram/Eprom and run them and find out IF there is a Bad IC on the Board or a bad connection or IF I have Bad Code.. But, I don't want to go thru the process of programming another Eprom every time I need or want to make a code change... I had the article before and even built it and then after not needing it for a long time I unwrapped it and used the sockets for someting else.
THANK YOU Marty
Click to expand...
I love non-volatile RAM chips like the Dallas DS 1220Y and 1225Y (16 & 64K) chips, but of course you have to have a way to get the data into them and modify it.

Check the Circuit Cellar index; at a fast look for 'emulators' I found 3 or 4 without looking; maybe one of those is the one you're thinking of? Also try searching for 'ICE'.

http://www.dtweed.com/circuitcellar/caj00030.htm
 
Hi All;
I found the Article, it was right where I thought it should be, only it was stuck to some other Papers, and So I din't see it.. The Title is -- Build the Emulo-8 By Stuart R. Ball Byte Magazine Aprril 1986..
I will Scan it tomorrow morning into a Pdf file format... And If someone can tell me How/If it is possible I will upload it for others to use...
THANK YOU Marty
 
There have to be about 42.5 jillion EPROM emulators out there. One of the simplest uses a Dallas Smart Socket RAM with a switch to disable writing.

One of the problems with the vintage stuff is that there are cheaper ways to do the job today. If I were doing, say, a 2764 (8Kx8 ) emulator, I'd probably use a small microcontroller and a dual-port SRAM such as a Cypress CY7C144E. The microcontroller can read and write independently of whatever the test system is doing. Modern microcontrollers have a variety of I/O interfaces, from simple parallel I/O to USB, EIA, and even ethernet. I'm surprised not to find something like this in production.
 
I guess Stuart Ball is one of Steve Ciarcia's aliases? ;-)

A lot of Bytes have already been scanned, but unfortunately not that one; thought I might have it in my collection but there's a gap there as well. I've got a few 8085 systems but all my S100 stuff is either Z-80 or 680x0; the only S100 SBC I've got is a Vector Graphic ZCB, the rest is Cromemco.

I think your PDFs will be too large to upload so you'd have to park them somewhere like Flicker etc. and provide a link.

As a matter of fact I'm just working on something similar for a 6502 system, but instead of a serial link I'm planning to just connect directly from one system's (EP)ROM socket to the other (through a MUX of course); we'll see how it works.
 
Chuck(G) said:
There have to be about 42.5 jillion EPROM emulators out there. One of the simplest uses a Dallas Smart Socket RAM with a switch to disable writing.
Click to expand...
Well, as I said I like the Dallas NVRAMs, pretty well the same as the Smart Socket + SRAM; I have a sandwich socket somewhere with a jumper to en/disable writing if necessary.

One of the problems with the vintage stuff is that there are cheaper ways to do the job today. If I were doing, say, a 2764 (8Kx8 ) emulator, I'd probably use a small microcontroller and a dual-port SRAM such as a Cypress CY7C144E. The microcontroller can read and write independently of whatever the test system is doing. Modern microcontrollers have a variety of I/O interfaces, from simple parallel I/O to USB, EIA, and even ethernet. I'm surprised not to find something like this in production.
Click to expand...
Actually, most of the units out there these days do seem to use a microcontroller that sort of emulates the dual-port function, at least the ones I've looked at (both hobby and commercial).
 
MikeS said:
I love non-volatile RAM chips like the Dallas DS 1220Y and 1225Y (16 & 64K) chips, but of course you have to have a way to get the data into them and modify it.
Click to expand...

Check out Ferroelectric RAM (FeRAM) as well. RAMtron sells several 5-volt compatible JEDEC pinout devices. It's basically core on silicon (it's even destructive read!). You get the speed/rewrite capacity of static RAM, the nonvolatility of ROM (several decades retention life), but there's no battery backup.
 
Hi All;
I can't help it , I just like Old School. And it fits better with my old systems.. And it is something I know and can work with and I am comfortable with.. But, Thanks for the help and suggestions to ALL.. I will later put it into a PDF, its five pages long.. If anyone wants a copy, feel free to ask..
THANK YOU Marty
 
Hi All;
I have most of the card working, just got in the Uart I needed to complete it.. The card has a 2716 eprom on it , and the ram is a 2016/6116 which makes it so that, in the Ram Socket, I can plug in the 2716 for testing, that I have wired up everything correctly.. So, that is also why I am doing it this way...
THANK YOU Marty
 
Chuck(G) said:
Heck, if you're emulating old-school EPROMs, a modern microcontroller probably has enough speed to emulate the whole EPROM...
Click to expand...

It really depends on the uC. 250ns access time is 4 MHz / 125ns is 8 MHz. Even at 250 and using a 40MHz PIC32, you have to code the ISR in 10 total clock cycles or less.

I was looking at this idea before. It should be possible to get a SRAM in a TSSOP-2, a PIC32 in a QFN-28, and a mini or micro USB connector on a top side of a small PCB the size of a normal 28-pin EEPROM (.7 x 1.4 in). Then put tri-statable isolation buffers on the bottom side to allow dynamic reprogramming by the PIC. Diode OR'd USB power would keep the board up through resets. Would be a neat project, just I have to many projects atm.
 
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