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Email Required, but never shown. BTW, if the chips are equipment pulls as opposed to new parts, it’s possible that the “software protection” feature has previously been enabled.
28c644 The same diagram shows CE being asserted followed by OE for a read cycle. Sign up or log in Sign up using Google. I wrote a program for the Arduino Uno that writes data to the first 4 addresses and then reads the data back.
I have tested an earlier version of the above program with a static RAM chip and everything works datassheet. I understand the benefits of separating the code into subroutines and will probably do this, but for now I am just trying to get the byte write working.
Thanks for the response, supercat.
I’d recommend following that same sequence and also change your write sequence to follow the diagram on the following page.
I added ms delays between every control pin change and made sure the order was consistent with the datasheet, but still no luck.
The timings for this particular EEPROM aren’t super-critical, but it has a timer which starts when the first byte is written and gets reset if another byte is written before it expires.
Mar 27 ’13 at Since I am only using the first three address pins, the rest are tied low. Sign up using Email and Password.
(Datasheet) 28C64 pdf – 64K CMOS EEPROM (1-page)
Also, I would suggest that you should write a writebyte procedure which sets all address and data wires to output and puts proper values on them, ensures WE and OE are deasserted, asserts CE, asserts and release WE, and releases CE, and a readbyte procedure which sets all address wires to output and puts proper values on them, sets all data wires to input, asserts CE and OE, samples all the data wires, and releases CE and OE.
That might help things. The chips are new, and I actually have two from two different manufacturers. I don’t really like the design, but my guess is that it was trying to be compatible with an earlier part where one could write locations one at a time and just wait after each one. Any help would be much appreciated. Looking at the datasheet on page 12 it shows a timing diagram and Chip Enable Access Time can be up to nS.
Initializing pins for write I have tied the top 10 address bits low and am only using the first 3 for now. If it has, you’ll need to wire up all your address wires in order to disable it. I am using the Xicor 28C64AP chip datasheet.
28C64A-15 – 28C64A 64K 150ns Parallel EEPROM Technical Data
When the timer expires, an internal write cycle is triggered and additional writes before it completes. All behave the same. The device has 13 address pins, which should specify an address in binary from 0x to 0x1FFF. Here is the serial output. Thanks for the info.