Read up to 24 bits (num_bytes) of SPI flash status register contents
        via RDSR, RDSR2, RDSR3 commands

        Not all SPI flash supports all three commands. The upper 1 or 2
        bytes may be 0xFF.

def read_status(self, num_bytes=2):
        """Read up to 24 bits (num_bytes) of SPI flash status register contents
        via RDSR, RDSR2, RDSR3 commands

        Not all SPI flash supports all three commands. The upper 1 or 2
        bytes may be 0xFF.
        """
        SPIFLASH_RDSR  = 0x05
        SPIFLASH_RDSR2 = 0x35
        SPIFLASH_RDSR3 = 0x15

        status = 0
        shift = 0
        for cmd in [SPIFLASH_RDSR, SPIFLASH_RDSR2, SPIFLASH_RDSR3][0:num_bytes]:
            status += self.run_spiflash_command(cmd, read_bits=8) << shift
            shift += 8
        return status