bq25040 - Trouble Getting Desired Modes Using EN/SET Pin

I have been using the bq25040 successfully with its default mode.  I now need to be able to switch to the USB100 mode.  However, in spite of giving the chip either two or four pulses on the EN/SET line, it still charges at the ISET current, which is around 250mA.  Our R_ISET = 2k Ohms, and R_IFULL = 1k Ohms.

The four-pulse waveform as sampled from the EN/SET line via an oscilloscope shows:

1. EN/SET high for many milliseconds (high = 1.8V)
2. EN/SET falls to ~0V and stays there for 320 microseconds
3. EN/SET goes high (1.8V) for 420 microseconds
4. EN/SET goes low (0V) for 420 microseconds
5. EN/SET goes high for 420 microseconds
6. EN/SET goes low for 420 microseconds
7. EN/SET goes high for 420 microseconds
8. EN/SET goes low for 330 microseconds
9. EN/SET goes high for 400 microseconds
10. EN/SET goes low for more than 4 milliseconds

My reading of the bq25040 datasheet indicates that this should put the bq25040 into USB100 mode, and limit the charging current to 100mA.  However, it is at 250mA after this sequence.

Is there something I have overlooked?  Something I'm misunderstanding?  An errata?

Thanks very much,

Chris