2020/09/12 20:49:51
Hi!  I purchased the A version of the chip by mistake.  It seems the only difference is the config register bit 1.  It always reads as IOC and BPNV  set, which it should be at power up.  I'm able to do the JEDEC read command, and get the correct results.  I can set and clear the WREN bit in the status register (and read it back), so I know the SPI bus is working.  I also have other chips on the board that I can read/write via spi, so that's all good.  I thought by writing the config bits I'd be able to reset the IOC bit to enable the WP and HOLD pins, but I cannot.  I'm trying to use the part in SPI single bit mode, and since I'm reading/writing some things it seems to be working.  I am unable to do an erase or write of any kind; I never get a busy bit, pretty sure it's because of WP not being enabled.  I replaced the part, same result.  I've used the predecessor part SST25VF064 in another product so I thought this would be a slam dunk!!  So, sorry for the long prelude, is the IOC bit always set (not able to set to zero) in the A version, and is it preventing me from erasing/writing in single bit SPI?
2020/09/12 22:33:58
Did you see this in the Data Sheet? This may help:
The I/O Configuration (IOC) bit re-configures the I/O
pins. The IOC bit is set by writing a ‘1’ to Bit 1 of the
Configuration register. When IOC bit is ‘0’ the WP# pin
and HOLD# pin are enabled (SPI or Dual Configuration
setup). When IOC bit is set to ‘1’ the SIO2 pin and SIO3
pin are enabled (SPI Quad I/O Configuration setup).
The IOC bit must be set to ‘1’ before issuing the following
SPI commands: SQOR (6BH), SQIOR (EBH),
RBSPI (ECH), and SPI Quad page program (32H).
Without setting the IOC bit to ‘1’, those SPI commands
are not valid. The I/O configuration bit does not apply
when in SQI mode. The default at power-up for
SST26VF064B is ‘0’ and for SST26VF064BA is ‘1’. 
Best regards,

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2020/09/13 09:06:14
Hi Ken, thanks for the super quick reply!!  I did see that, but I was hoping that one could simply write the config register and set that bit to zero.  If you have the non A part that has the IOC bit preset to zero at power up, AND you can program it to a 1, then I assumed (was hoping) that the reverse would apply and I'd be able to programmatically set it to 0.  All the register info says it is read/write.  I didn't see any restrictions regarding the IOC bit for the A part except for the preset.  Microchip could have made it easy by stating at the top of the data sheet that the A part has certain non alterable presets.  Oh, well, non A parts have been ordered!
Again, thanks for the quick response!
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