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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
155 of 1441
NXP Semiconductors
UM10503
Chapter 11: LPC43xx/LPC43Sxx Configuration Registers (CREG)
11.4.17 USB1 frame length adjust register
Remark:
This register is only implemented for parts with on-chip flash. See
.
The USB frame length adjust register is used to adjust any offset from the clock source
that generates the clock that drives the SOF counter. When a new value is written into
these six bits, the length of the frame is adjusted. Its initial programmed value is
system-dependent based on the accuracy of hardware USB clock. This register should
only be modified when the HCH bit in the USB STS register is one. Changing value of this
register while the host controller is operating yields undefined results.
This register should not be reprogrammed by USB system software unless the default
values are incorrect, or the system is restoring the register while returning from a
suspended state.
Remark:
The FLADJ register must be read only after initializing the USB interface.
Reading this register before initialization of the USB causes the MCU to stall.
For details on using the SOF signal, see
Table 112. USB0 frame length adjust register (USB0FLADJ, address 0x4004 3500) bit
description
Bit
Symbol
Description
Reset
value
Access
5:0
FLTV
Frame length timing value
The frame length is given in the number of high-speed bit
times in decimal format. Each decimal value change to this
register corresponds to 16 high-speed bit times. The SOF
cycle time (number of SOF counter clock periods to
generate a SOF micro-frame length) is equal to 59488 +
value in this field. The default value is decimal 32 (0x20),
which results in a SOF cycle time of 60000.
0x00 = 59488 (= 59488 + 0 x 16)
0x01 = 59504 (= 59488 + 1 x 16)
0x02 = 59520 (= 59488 + 2 x 16)
...
0x1F = 59984 (= 59488 + 31 x 16)
0x20 = 60000 (= 59488 + 32 x 16)
...
0x3E = 60480 (= 59488 + 62 x 16)
0x3F = 60496 (= 59488 + 63 x 16)
0x20
R/W
31:6
-
Reserved
-
-