For Interrupt and Isochronous transfers, this field defines the polling interval
for the endpoint. For Bulk end- points,this field sets the number of
frames/microframes after which the endpoint should time out on receiving a
stream of NAK responses.
The following table describes the valid values and interpretation for these
bits:
| Transfer Type | Speed | Valid Values (m) | Interpretation |
|---|
| Interrupt | Low/Full | 0x01 to 0xFF | Polling interval is 'm'
frames. |
| High | 0x01 to 0x10 | Polling interval is
2(m-1) frames. |
| Isochronous | Full or High | 0x01 to 0x10 | Polling interval is
2(m-1) frames/microframes. |
| Bulk | Full or High | 0x02 to 0x10 | NAK limit is 2(m-1)
frames/microframes. A value of '0' or
'1' disables the NAK time-out
function. |
