> Now i see that Mchip have different SPI and Microwire EEPROMS
> And also there seem to be different modes in SPI
> What is the difference?

Hi Morgan,

A good tutorial on the differences between SPI, Microwire and
I2C EEPROMs is "Using Serial EEPROMs" by Jan Axelson, on Circuit
Cellar Ink #84 (July 1997).

There is also a second part (CCI #85) describing a project of
an EEPROM programmer connected on the parallel port of a PC,
complete with VB code that can be downloaded from the CCI site:
ftp://ftp.circuitcellar.com/CCINK/1997/Issue_85/SEEPROM.ZIP

If I recall correct, the main differences between SPI and Microwire
are:

- Chip Select:
  SPI is active low.
  Microwire is active high and the master must deactivate CS after
  each instruction (except sequential reads)

- Clock edge:
  SPI and Microwire both write bits (EEPROM SO/DO line) on the
  rising edge of the clock, but they differ when reading bits
  (EEPROM SI/DI line): SPI latch data on the FALLING edge of the
  clock, while Microwire on the RISING edge.
- There are also other (small?) differences in the protocol

Adriano