SDA
SETBITS(SDA | SCL);
SETBITS(SDA | 0);
SETBITS(SDA | SCL);
if (READ & SDA)
SETBITS(SDA | 0);
bit = (flags & I2C_F_LAST) ? SDA : 0;
bit = (val & mask) ? SDA : 0;
SETBITS(SDA | SCL);
error = (READ & SDA) ? EIO : 0;
SETBITS(SDA | 0);
SETBITS(SDA | SCL);