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2 wire serial EEPROM and 9901


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#1 InsaneMultitasker OFFLINE  

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Posted Sun Aug 5, 2018 8:48 PM

Does anyone here have experience with 2-wire serial EPROMs?  I'm looking for one that could easily interface with the 9901.  While I could probably squeak by with 128 bytes, I would certainly not be opposed to larger sizes up to 256K.   What I'd like to do is connect the clock and serial data pins to the 9901, using two unused pins.  I'd then use the serial eeprom to store configuration information for the Geneve and its devices.  

 

20-odd years ago Jim S. had interfaced a serial eprom to the Geneve to provide Cecure a hardware-based copy protection.  Thus I know a 2-wire device can be implemented, I just don't know what is available today that might work well for this application. 

 



#2 Stuart OFFLINE  

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Posted Mon Aug 6, 2018 2:01 AM

If you're talking about an I2C EEPROM, you can implement an I2C interface easily on a 9901 - I done one using the joystick port.

 

http://www.stuartcon...m#i2c_interface

 

https://learn.sparkf...-serial-eeproms

 

Edit: Ideally you'll need *three* unused pins on the 9901 to implement an I2C interface: one to drive the clock, one to output data, and another to input data - because once you programme a pin on the 9901 as an output, you can't use it again as an input unless you do a hard or soft reset of the 9901. You might be able to get away with doing a soft reset at the point where you want to switch between reading and writing the interface, depending on what happens to the clock output at the point you do the reset (will it float high or low, and what does the I2C interface expect on the clock output at that point?), and what other things are connected to the 9901.


Edited by Stuart, Mon Aug 6, 2018 7:46 AM.


#3 InsaneMultitasker OFFLINE  

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Posted Mon Aug 6, 2018 11:10 PM

Thanks, Stuart, I'll take a closer look at your site.  Here is one of the snips of code I came across. The routine appears to use three CRU bits. I cannot find any records that indicate which chip was used back then, but the concept seems to be similar to what you describe.  Knowing the I2C interface works well is already one step ahead of where I was the other day :) 

 

Spoiler


#4 Willsy OFFLINE  

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Posted Tue Aug 7, 2018 1:04 AM

I'm using FRAM in my designs at work. I've stopped bothering with Flash completely.

 

Some devices: 

  • Fujitsu MB85RC256V - 32x8 bit I2C FRAM - 2.0 V to 3.6 V
  • Fujitsu MB85RC128 - 16kx8 bit I2C FRAM - 2.7 V to 3.6 V
  • Cypress FM24V10 - 1-Mbit 128K × 8 Serial I2C F-RAM - 2.7 V to 5.5 V

FRAM (a Texas Instruments invention) has considerable advantages over Flash memory:

  • High-endurance 100 trillion (10 ) read/writes
  • 151-year data retention
  • No-Delay writes
  • Advanced high-reliability ferroelectric process
  • No complex page setup/incantations to write to memory - for reads and writes, the devices are addressable at the byte level; there's no page-level wear-management issues to worry about

All of the above devices at simple 8-pin devices. They are surface mount but there are little adaptor boards available if you want to use 2.54mm DIL.

 

Data sheets attached.

 

Have fun :-)

 

Attached File  FM24V10 128Kx8 I2C FRAM Datasheet.pdf   1.9MB   9 downloads

Attached File  Fujitsu-MB85RC128PNF-G-JNE1-datasheet.pdf   595.43KB   6 downloads

Attached File  MB85RC256V.pdf   1.43MB   6 downloads



#5 FarmerPotato OFFLINE  

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Posted Tue Aug 7, 2018 10:02 AM

I've been a fan of FRAM ever since I wandered by the lab door of RamTron at UCCS.
Texas Instruments has licensed it and brought it into the mainstream after 30 years.
 
Here is a neat TI LaunchPad board with '430 CPU with on-chip FRAM that can run several flavors of FORTH.
It often goes on sale for $4.30
 


#6 TheBF OFFLINE  

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Posted Wed Aug 8, 2018 7:59 AM

I'm using FRAM in my designs at work. I've stopped bothering with Flash completely.

 

Some devices: 

  • Fujitsu MB85RC256V - 32x8 bit I2C FRAM - 2.0 V to 3.6 V
  • Fujitsu MB85RC128 - 16kx8 bit I2C FRAM - 2.7 V to 3.6 V
  • Cypress FM24V10 - 1-Mbit 128K × 8 Serial I2C F-RAM - 2.7 V to 5.5 V

FRAM (a Texas Instruments invention) has considerable advantages over Flash memory:

  • High-endurance 100 trillion (10 ) read/writes
  • 151-year data retention
  • No-Delay writes
  • Advanced high-reliability ferroelectric process
  • No complex page setup/incantations to write to memory - for reads and writes, the devices are addressable at the byte level; there's no page-level wear-management issues to worry about

All of the above devices at simple 8-pin devices. They are surface mount but there are little adaptor boards available if you want to use 2.54mm DIL.

 

Data sheets attached.

 

Have fun :-)

 

attachicon.gifFM24V10 128Kx8 I2C FRAM Datasheet.pdf

attachicon.gifFujitsu-MB85RC128PNF-G-JNE1-datasheet.pdf

attachicon.gifMB85RC256V.pdf

 

 

These are new to me, being out of the industry for 20 years.  

 

Do you use these like disk and read the data into RAM at startup?

 

Does anybody make them with address/data buss access like static RAM?

(maybe not needed, if they are fast enough using serial)

 

B



#7 RickyDean OFFLINE  

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Posted Wed Aug 8, 2018 8:41 AM

 

 

These are new to me, being out of the industry for 20 years.  

 

Do you use these like disk and read the data into RAM at startup?

 

Does anybody make them with address/data buss access like static RAM?

(maybe not needed, if they are fast enough using serial)

 

B

Sounds like a new version of SAMS to me. ;)



#8 Willsy OFFLINE  

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Posted Wed Aug 8, 2018 9:41 AM

 

 

These are new to me, being out of the industry for 20 years.  

 

Do you use these like disk and read the data into RAM at startup?

 

Does anybody make them with address/data buss access like static RAM?

(maybe not needed, if they are fast enough using serial)

 

 

 

No, you literally use them as RAM. Read/Write from/to them as you want with impunity. The only difference is they are serial devices (I haven't seen one with a parallel address/data bus).

 

When the power goes off they retain their contents, unlike traditional ram.

 

The "F" in FRAM refers to "ferro". Remember those old magnetic core, or "bubble" memories? The FRAM is based on the same technology, just scaled right down to the micron level. Incredible.

 

You can't get anything like the density of modern DDR type "computer" memory. The biggest I've seen is 128KB, but for embedded projects that's perfect. Flash is a major pain the a$$ to work with.



#9 Willsy OFFLINE  

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Posted Wed Aug 8, 2018 9:43 AM

I spoke too soon... Fujitsu now have a part with a "traditional" parallel address/data bus and 4mbit capacity.

 

Neat.






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