interfacing a old fashioned 2716-2764 eprom to prop chip

mikediv

Hey guys has anyone here ever interfaced the older type erpoms 2716-2764,27256 I have a bunch of them I mean a bunch 20 of each at least and wanted to install some spin programs into one and then boot it from the prop as a stand alone configuration for an offsite control projects , if anyone has done it and is willing to share I would love to see some examples
I tried connecting with the 1K resistor deal to the data and address lines I burned a very simple blink led program to see if the prop would boot but no luck.

kwinn

I have used these chips extensively with 5V logic and micros, but not in 3.3V systems. If the CE and OE lines are pulled low you should get data from some memory location out. It may be that the 3.3V high level is not high enough, or that the access time is longer than you are allowing. The older eproms were slow (~1usec).

Try waiting 2 microseconds after outputting the address and pulling CE and OE low before reading the eprom.

Try filling the chip with 10101010/01010101 so that the output pins toggle as you step through the addresses and see what you get.

Try using a cmos buffer connected to 5V for the address, data, and CE/OE pins

kwinn

PS if you only want to use it for loading programs you may want to look at the 74hc4040 counter, 74hc595 latched serial to parallel shift register, or 74as867/9 presetable up down counter for addressing and the 74hc165 parallel to serial shift register to input the data. Cuts down on the number of i/o pins required.

Leon

I made an EPROM programmer many years ago using a Z80 and 4040 counter. I'd bin them and use flash memory instead, it's much easier.

Leon

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mikediv

Thanks guys Leon I know they are pretty primitive but like I said I have lots of them and I just like building stuff it help m eunderstand whats really going on. All I wanted to do was prove my concept I did not use any support chips basicly wired up the entire eprom to the prop and then tried to write a program that would load the small program from eprom to th eprop and then execute it, but as simple as it seems its turning out to be far more complicated than I thought. just reading every single address to load the code by hand even the smallest led blinking program has a·load of lines of code I would have loved to see it done though

Post Edited By Moderator (Chris Savage (Parallax)) : 1/22/2009 10:06:01 PM GMT

kwinn

mikediv, if you have something that can burn the program into the 27xx chip the hardware to read it is trivial. The Q1 of the 4040 goes to A0 of the 27xx, Q2 to A1, etc. connect the 4040 and the 27xx to ground and +5V, and use 1K resistors on all pins from the prop to the 4040 and 27xx.
Hardware:
Connect eight pins (P0-P7 assumed) from the prop to D0-D7 of the 27xx through 1K resistors.
Connect one pin (P8 assumed) from the prop to the reset pin (11) of the 4040 through a 1K resistor.
Connect one pin (P9 assumed) from the prop to the clock pin (10) of the 4040 through a 1K resistor.
Software:
Set P0-P7 to inputs
Set P8-P9 to outputs
Set P11 low to reset the 4040
Wait 100 nsec
Set P11 high to allow counting
For count = 1 to sizeofeprom
Wait for 1 usec
Read data on P0-P7
Do what you want to do with the data
Set P10 high
Wait for 100 nsec
Set P10 low
Go to For count statement

For very old chips you may have to increase the waits in the loop. This should read a 4K eprom in less than 5 msec. If you have eproms larger than 4K you will need to add a second 4040 which will get you up to 16 megabytes.

Post Edited (kwinn) : 1/22/2009 11:41:46 PM GMT

mikediv

kwinn·that is awesome thank you very much, I do have a bunch of differant eprom burners for the pc I can read write pretty much any of the older style eproms. This is just the info I wanted and needed thanky you again.
Just one other thing One of the problems I am running into is making spin code readable for my burner I can load Ascii . or Bin files the problem I am having is I have nothing to compile spin output to a bin file? example take the simple LED blinking program when I save it from the spin editor it save it as a spin file if I try and burn that file to eprom I dont think its the right way the erpom burner software will load a spin file i.e"test.spin" but when you looked at the disasembled code it does not seem to be even close
maybe I can find a compiler for spin to turn it into bin. also I hate to bug you but do you know of any sample programs in either Prop or BS2 that would let me read the code into any of these chips"prop basic stamp2"??
Thanks again
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