Register Descriptions
1389
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Universal Serial Bus (USB) Controller
18.5.41 USB Host Transmit Interval Endpoint n Register
(USBTXINTERVAL[1]USBTXINTERVAL[15])
The USB host transmit interval endpoint
n
8-bit registers (USBTXINTERVAL[
n
]), for interrupt and
isochronous 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 USBTXINTERVAL[
n
] registers values define a number of frames, as follows:
Table 18-55. USBTXINTERVAL[n] Frame Numbers
Transfer Type
Speed
Valid Values (m)
Interpretation
Interrupt
Low-speed or Full-speed
0x01-0xFF
The polling interval is
m
frames.
Isochronous
Full-speed
0x01-0x10
The polling interval is 2
(m-1)
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.
For the specific offset for each register see
.
Mode(s):
OTG A or Host
The USBTXINTERVAL[
n
] registers are shown in
and described in
.
Figure 18-52. USB Host Transmit Interval Endpoint n Register (USBTXINTERVAL[n])
7
0
TXPOLL / NAKLMT
R/W-0
LEGEND: R/W = Read/Write; -
n
= value after reset
Table 18-56. USB Host Transmit Interval Endpoint n Register(USBTXINTERVAL[n])
Field Descriptions
Bit
Field
Value
Description
7-0
TXPOLL /
NAKLMT
0
TX Polling / NAK Limit The polling interval for interrupt/isochronous transfers; the NAK limit for bulk
transfers. See
for valid entries; other values are reserved.