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. |
