regarding your two tricky questions, let me try to explain the date sheet features for our customers more in detail:
M1 and M2 is the different pitch distance between 150 mil (closer together) and 200 mil of the pins – so the layout of the PCB must be different
as the references from Macronix are finishing either with I02 or I03 there is a difference in the STR (Single Transfer Rate up to 80 MHz) configuration: with I02 it needs to be done in H/W (Hard-Ware) for MX25V16066M1I02 and MX25V16066M2I02
MX25V1606FM1I03 supports also DTR (Double Transfer Rate) up to 104 MHz with Dual I/O (In/Output) configuration in Soft-Ware (SW)
The MX25xxx06 series provides Standard Serial Interface x1 or x2 I/O [Single I/O or Dual I/O] at a single 3V or 2.5V power-supply voltage. All these products are offered with 4kByte sectors and 64kB blocks.
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