25LC256 eeprom - Electronic Circuits Projects Diagrams Free

mikesmixes777 · 6th February 2008, 01:59 PM

I am busy with an embedded web server, based on the TCP Stack 3.75.7e from Jorge.

I am using the PIC18LF2620, ENC28J60 and 25LC256 eeprom. I dont need a level shifter as the SPI is all 3.3Vdc.

Can I run the eeprom with Vcc=3.3Vdc without effecting the frequency that the main stack code uses. Also, can all the pins on the eeprom operate with 3.3Vdc?

Thanks
Michael

blueroomelectronics · 6th February 2008, 02:10 PM

My next kit is very similar, although I'm running the EEPROM at 5V.
According to the 25LC256 datasheet the maximum FCLK is 5MHz at 3.3V and 10MHz at > 4.5V
All the pins will work down to 2.5V
Jorges stack is excellent, nice fellow too.
Is your board homemade or a kit?

mikesmixes777 · 6th February 2008, 02:19 PM

My board is homemade. I sat for hours designing the tracks and only had the fascility of a single-sided PCB manufacturer, for proto type (it was free). I shall get the proper pcb (double sided) made when Im ready.

It was only about 2months later that I came across Jorge's website and all his projects. i almost fell off my chair to see the various circuits, which were so similar to mine. Mine is almost the same as the eip-10T project. I was designing mine originally using the PIC18LF252, however I just received my PIC18LF2620 samples today

Can you run the eeprom at 5Vdc and still use the SPI with 3.3V signals?

blueroomelectronics · 6th February 2008, 02:53 PM

Well then, I've been trying to recruit a handful of members to help with my Ladybug design. I try to make it worth their while. Search for Ladybug on these forums and contine a thread I'll post all my designs there. I am going to have production qty PCBs made. I have a working handwired prototype minus the I/O section. And PCB artwork has been started.
The ENC28J60 designs never stray far from the Microchip reference design.

Quote:

Can you run the eeprom at 5Vdc and still use the SPI with 3.3V signals?

Good question, not sure.

mikesmixes777 · 6th February 2008, 03:22 PM

I shall have a look at that and let you know.

ya I wonder if u can run the eeprom at 5v and use the 3.3v signals. Anyone else know??

jacob.zurasky · 7th February 2008, 05:42 AM

I never have tried it, but on page 2 of the datasheet, it states the high-level input voltage needs to be a minimum of 0.7Vcc, so 3.5v for 5v.

mikesmixes777 · 7th February 2008, 06:29 AM

I just read that in the datasheet aswell. Well that explains it all.

Thanks
Mike

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6th February 2008, 01:59 PM	(permalink)
mikesmixes777	25LC256 eeprom I am busy with an embedded web server, based on the TCP Stack 3.75.7e from Jorge. I am using the PIC18LF2620, ENC28J60 and 25LC256 eeprom. I dont need a level shifter as the SPI is all 3.3Vdc. Can I run the eeprom with Vcc=3.3Vdc without effecting the frequency that the main stack code uses. Also, can all the pins on the eeprom operate with 3.3Vdc? Thanks Michael __________________ "//Some day we'll look back and Laugh"

6th February 2008, 02:10 PM	(permalink)
blueroomelectronics	My next kit is very similar, although I'm running the EEPROM at 5V. According to the 25LC256 datasheet the maximum FCLK is 5MHz at 3.3V and 10MHz at > 4.5V All the pins will work down to 2.5V Jorges stack is excellent, nice fellow too. Is your board homemade or a kit? __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

6th February 2008, 02:19 PM	(permalink)
mikesmixes777	My board is homemade. I sat for hours designing the tracks and only had the fascility of a single-sided PCB manufacturer, for proto type (it was free). I shall get the proper pcb (double sided) made when Im ready. It was only about 2months later that I came across Jorge's website and all his projects. i almost fell off my chair to see the various circuits, which were so similar to mine. Mine is almost the same as the eip-10T project. I was designing mine originally using the PIC18LF252, however I just received my PIC18LF2620 samples today Can you run the eeprom at 5Vdc and still use the SPI with 3.3V signals? __________________ "//Some day we'll look back and Laugh"

6th February 2008, 03:22 PM	(permalink)
mikesmixes777	I shall have a look at that and let you know. ya I wonder if u can run the eeprom at 5v and use the 3.3v signals. Anyone else know?? __________________ "//Some day we'll look back and Laugh"

7th February 2008, 05:42 AM	(permalink)
jacob.zurasky	I never have tried it, but on page 2 of the datasheet, it states the high-level input voltage needs to be a minimum of 0.7Vcc, so 3.5v for 5v.

7th February 2008, 06:29 AM	(permalink)
mikesmixes777	I just read that in the datasheet aswell. Well that explains it all. Thanks Mike __________________ "//Some day we'll look back and Laugh"