The USB host receive polling interval endpoint n 8-bit registers (USBRXINTERVAL[n]), for interrupt transfers, define the polling interval for the currently selected transmit endpoint. For bulk endpoints, this register defines the number of frames after which the endpoint should time out on receiving a stream of NAK responses.
The USBRXINTERVAL[n] registers values define a number of frames, as follows:
Table 22-57 USB Host Receive Polling Interval Endpoint
n Registers (USBRXINTERVAL[n]) Frame NumbersTransfer Type | Speed | Valid Values (m) | Interpretation |
---|
Interrupt | Low-speed or Full-speed | 0x01-0xFF | The polling interval is m frames. |
Bulk | Full-speed | 0x02-0x10 | The NAK Limit is 2(m-1) frames. A value of 0 or 1 disables the NAK timeout function. |
The USBRXINTERVAL[n] registers are shown in Figure 22-51 and described in Table 22-53.
Figure 22-54 USB Host Receive Polling
Interval Endpoint n Registers (USBRXINTERVAL[n])
LEGEND: R/W = Read/Write; -n = value after
reset |
Table 22-58 USB Host Receive Polling
Interval Endpoint n Registers (USBRXINTERVAL[n]) Field
DescriptionsBit | Field | Value | Description |
---|
7-0 | TXPOLL / NAKLMT | 0 | TX Polling / NAK Limit The polling interval for interrupt transfers; the NAK limit for bulk transfers. See Table 22-57 for valid entries; other values are reserved. |