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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
665 of 1441
NXP Semiconductors
UM10503
Chapter 25: LPC43xx/LPC43Sxx USB0 Host/Device/OTG controller
25.6.12 BINTERVAL register
This register defines the bInterval value which determines the length of the virtual frame
(see
). The BINTERVAL register divides the SOF signal by the value BINT.
Remark:
The BINTERVAL register is not related to the bInterval endpoint descriptor field
in the USB specification.
Table 485. USB Transfer buffer Fill Tuning register in host mode (TXFILLTUNING - address 0x4000 6164) bit
description
Bit
Symbol
Description
Reset
value
Access
7:0
TXSCHOH
FIFO burst threshold
This register controls the number of data bursts that are posted to the TX
latency FIFO in host mode before the packet begins on to the bus. The
minimum value is 2 and this value should be a low as possible to maximize
USB performance. A higher value can be used in systems with unpredictable
latency and/or insufficient bandwidth where the FIFO may underrun because
the data transferred from the latency FIFO to USB occurs before it can be
replenished from system memory. This value is ignored if the Stream Disable
bit in USBMODE register is set.
0x2
R/W
12:8
TXSCHEATLTH
Scheduler health counter
This register increments when the host controller fails to fill the TX latency
FIFO to the level programmed by TXFIFOTHRES before running out of time
to send the packet before the next Start-Of-Frame .
This health counter measures the number of times this occurs to provide
feedback to selecting a proper TXSCHOH. Writing to this register will clear the
counter. The maximum value is 31.
0x0
R/W
15:13
-
Reserved
-
-
21:16
TXFIFOTHRES
Scheduler overhead
This register adds an additional fixed offset to the schedule time estimator
described above as T
ff
. As an approximation, the value chosen for this register
should limit the number of back-off events captured in the TXSCHHEALTH to
less than 10 per second in a highly utilized bus. Choosing a value that is too
high for this register is not desired as it can needlessly reduce USB utilization.
The time unit represented in this register is 1.267
s when a device is
connected in High-Speed Mode for OTG and SPH.
The time unit represented in this register is 6.333
s when a device is
connected in Low/Full Speed Mode for OTG and SPH.
0x0
R/W
31:22
-
Reserved
Table 486. USB BINTERVAL register (BINTERVAL - address 0x4000 6174) bit description
Bit
Symbol
Description
Reset
value
Access
3:0
BINT
bInterval value (see
)
0x00
R/W
31:4
-
Reserved
-
-