Post by thread:Does SPI mode work?

>>Microchip are quite good at choosing useful peripherals >>(I2C, PSP) but unfortunately not very good at >>designing them properly or documenting them. Here!! Here!! I'm using a 16C74A talking to a Micro-Chip 24C16 and have never gotten the SPI mode to work. Looking at their applications notes, it is easy to detect a large amount of kludging going on by Micro-Chip (and their juinor high apps note writers). Of course, their app note doesn't work either...unless I'm missing something. I'm using a Logic analyizer and a 2 GS/s storage scope so I have a good feel for what the signals are doing. They never look right for any of the control settings. Mean while, I'm bit banging the data out just fine, only a little slow.... Just wondering. Thanks, Ralph

Hello, I too, am having some problem with SPI. I'm using a PIC16C63 and trying to talk to a Xicor X25128 SPI EEPROM. I think I'm able to write to it okay but I not so sure about reading using SPI. I write "ABCDEFGHI" but I only read "ACEG" How do I make the PIC continue to clock the SCK line without writing first? Do I just continue to read the SSPBUF to toggle the SCK? -Randie > {Original Message removed}

>I too, am having some problem with SPI. > >I'm using a PIC16C63 and trying to talk to a Xicor X25128 SPI EEPROM. I >think I'm able to write to it okay but I not so sure about reading using >SPI. I write "ABCDEFGHI" but I only read "ACEG" I believe this might be caused by the write delay all EEPROMs have, it take s a few milliseconds to write to EEPROM, and if you try to write another byte wh ile the unit is still actually storing the previous byte it will not get written . Why I say this is because you say you write ABCDEFG and only get back ACEG, w ell it seems that while you told it to write the B, D, and F it was still writin g the previous byte, A, C, E respectivly. Hope this helps. TTYL -----== Sent via Deja News, The Discussion Network ==----- http://www.dejanews.com/ Easy access to 50,000+ discussion forums

> >I too, am having some problem with SPI. > > > >I'm using a PIC16C63 and trying to talk to a Xicor X25128 SPI EEPROM. I > >think I'm able to write to it okay but I not so sure about reading using > >SPI. I write "ABCDEFGHI" but I only read "ACEG" > > I believe this might be caused by the write delay all EEPROMs have, it ta kes a few milliseconds to write to EEPROM, and if you try to write another byte while the unit is still actually storing > > ayiiiiiiieeeeeeeeeeeeeeeeeeeee sounds like me too........... alice alice

At 00:08 01/19/99 -0800, Alice Campbell wrote: >> >I'm using a PIC16C63 and trying to talk to a Xicor X25128 SPI EEPROM. I >> >think I'm able to write to it okay but I not so sure about reading using >> >SPI. I write "ABCDEFGHI" but I only read "ACEG" >> >> I believe this might be caused by the write delay all EEPROMs have, >it takes a few milliseconds to write to EEPROM, and if you try to write >another byte while the unit is still actually storing > >> >ayiiiiiiieeeeeeeeeeeeeeeeeeeee >sounds like me too........... ayie... :-) i've never used SPI eeproms, but microwire (and i guess SPI, too) eeproms have a status bit that indicates that the eeprom is busy writing, and i2c eeproms don't ACK. as a matter of rule i check this bit (or for the ACK) if there's any chance that the next access might occur before the write cycle time. don't you? ge

Take a look at http://www.circellar.com, they have an article on there that is computing acceleration data from a model rocket. They use that xicor chip X25F128 and the pic's spi port. it's a very cool idea, I'm not sure if it works, but you might be able to extract some info from the accompanying code for help with your SPI port problems.... luck for everyone, Jon Ralph Stickley wrote: {Quote hidden}> > >>Microchip are quite good at choosing useful peripherals > >>(I2C, PSP) but unfortunately not very good at > >>designing them properly or documenting them. > > Here!! Here!! I'm using a 16C74A talking to a Micro-Chip 24C16 and have > never gotten the SPI mode to work. > > Looking at their applications notes, it is easy to detect a large amount > of kludging going on by Micro-Chip (and their juinor high apps note > writers). Of course, their app note doesn't work either...unless I'm > missing something. I'm using a Logic analyizer and a 2 GS/s storage > scope so I have a good feel for what the signals are doing. They never > look right for any of the control settings. > > Mean while, I'm bit banging the data out just fine, only a little > slow.... > > Just wondering. Thanks, > Ralph