Post by thread:SPI vs I2C

Antonio Almeida wrote: > > What's the difference between using an SPI or I2c EEPROM with the > PICs (ignoring the fact that one needs 3 and the other needs 2 wires)? > > Thanks. Hi, SPI works on higher speed (up to 1Mhz),I2C - 100Khz. SPI simplest exchange protocol (simple software). Saras.

Antonio Almeida wrote: > > What's the difference between using an SPI or I2c EEPROM with the > PICs (ignoring the fact that one needs 3 and the other needs 2 wires)? > > Thanks. Hi, SPI works on highest speed (up to 1Mhz),I2c - 100Khz. SPI simplest exchange protocol (simple software). I2C can handle many devices on same wires (with diferent slave addresses),SPI needs individual CS lines for eatch device. Saras.

> What's the difference between using an SPI or I2c EEPROM with the > PICs (ignoring the fact that one needs 3 and the other needs 2 wires)? SPI is normally rated up to 2MHz. IIC is normally rated up to 100kHz (though most manufacturers also supply 'high speed' devices rated up to 400kHz). Addressing of multiple devices is also different. SPI addresses each device using a discrete 'chip select' line, so you need as many CS's as you have devices. IIC, on the other hand, embeds the addressing in the data stream so _no_ additional lines are needed. Given that the high data rates are rarely needed, my own pref- erence is for IIC. ___Bob

Harris do 128 and 256 byte SPI RAM - CDP68HC68R1e and CDP68HCR2E respectively. -----Original Message----- From: Harold Hallikainen [SMTP:spam_OUTharoldhallikainenTakeThisOuTJUNO.COM] Sent: 06 April 1997 08:16 To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU Subject: Re: SPI vs I2C And.. it appears no one makes SPI RAMs, just EEPROMs, right? I searched all week and finally went with the Dallas RAMPort (thanks to the list!) for more memory. Harold Attachment converted: wonderland:WINMAIL.DAT 1 (????/----) (0000D942)

> And.. it appears no one makes SPI RAMs, just EEPROMs, right? I >searched all week and finally went with the Dallas RAMPort (thanks to the >list!) for more memory. I have a guy coming in from RAMTRON. It's RAM speed, EEPROM non-volatility, and pin compatible with various EEPROMs. http://www.ramtron.com Andy ================================================================== Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 Hardware & Software for Industry & R/C Hobbies "Go fast, turn right, and keep the wet side down!" ==================================================================

>Try PHILIPS >http://www.semiconductors.philips.com/ > > Saras. Phillips is a very poor choice for USA products. They have availability problems. Worse the Motorola, if that's possible. Andy ================================================================== Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 Hardware & Software for Industry & R/C Hobbies "Go fast, turn right, and keep the wet side down!" ==================================================================

>> And.. it appears no one makes SPI RAMs, just EEPROMs, right? I >> searched all week and finally went with the Dallas RAMPort (thanks to >> the list!) for more memory. > Harold > Harris do 128 and 256 byte SPI RAM - CDP68HC68R1e and CDP68HCR2E > respectively. Harold, I'm designing a product with a MCU with SPI and up to 512K bytes of non-volatile RAM. The RAM is from Dallas. I send the address by SPI to two S/R and then to address lines of RAM. Additional addressing lines (3) is provided direcly by MCU. The data path use a 8 bit port (shared with LCD module) to read and write data to RAM but you can do this also by SPI. My two cents (if worth to someone else) Luiz Marques

I've seen this URL posted numerous time to PICList. When I go there all I get is an advertisement for an ISP. Anyone else having this problem? Frank Richterkessing Experimental Methods Engineer GE Appliances FRANK.RICHTERKESSINGKILLspamAPPL.GE.COM {Quote hidden}> ---------- > From: Andy Kunz[SMTP:.....montanaKILLspam.....FAST.NET] > Sent: Monday, April 07, 1997 10:21AM > To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU > Subject: Re: SPI vs I2C > > > And.. it appears no one makes SPI RAMs, just EEPROMs, right? > I > >searched all week and finally went with the Dallas RAMPort (thanks to > the > >list!) for more memory. > > I have a guy coming in from RAMTRON. It's RAM speed, EEPROM > non-volatility, and pin compatible with various EEPROMs. > > http://www.ramtron.com > > Andy > > ================================================================== > Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 > Hardware & Software for Industry & R/C Hobbies > "Go fast, turn right, and keep the wet side down!" > ================================================================== >

>I've seen this URL posted numerous time to PICList. When I go there all >I get is an advertisement for an ISP. Anyone else having this problem? >> >> http://www.ramtron.com Well, yeah, I got the same message... But poke about a bit and the site tells you what to do (the essence of computing is experimentation, ie: poke about a bit). Try http://www.ramtron.com/ramtron By the way, you need a frames capable browser! ___Bob

On Mon, 7 Apr 1997 15:12:51 -0700 Luiz Marques <omarquesspam_OUTUFBA.BR> writes: >Harold, I'm designing a product with a MCU with SPI and up to 512K >bytes >of non-volatile RAM. The RAM is from Dallas. >I send the address by SPI to two S/R and then to address lines of RAM. >Additional addressing lines (3) is provided direcly by MCU. >The data path use a 8 bit port (shared with LCD module) to read and >write >data to RAM but you can do this also by SPI. This looks like a good approach for the amount of RAM you need. Since I only need 1K to 2K bytes or RAM, it appears a lower chip count approach is to use the Dallas RamPort (2 Kbytes). I'm surprised there aren't more larger SPI RAMs out there. I'd love to have a few Kbytes in an 8 pin package! Harold

This looks like a good approach for the amount of RAM you need. Since I only need 1K to 2K bytes or RAM, it appears a lower chip count approach is to use the Dallas RamPort (2 Kbytes). I'm surprised there aren't more larger SPI RAMs out there. I'd love to have a few Kbytes in an 8 pin package! I would like to see someone (anyone at Microchip listening?) produce a RAM chip with a synchronous serial input, the clock wire of which was designed to run off a small micro's XTAL signal directly (i.e. with an adjustible clock divider so the CPU could simply input or output a bit every, say, 12 oscil- lator clocks. Such a part would not be terribly hard to de- sign, but it would save an I/O pin (as compared with I2C-style) or two (compared with SPI) and it would be faster than either of those other protocols as well. Better still would be if Microchip could produce a PIC with a feature to input/output data on such a device at a rate of one bit per raw clock [each byte being sent as probably a 12-bit datagram]. The hardware would not be overly complex, but it would be able to transfer data almost as fast as a "wide" bus but at a fraction of the cost in pins and real estate. What does anyone think of this idea?