UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
220 of 362
NXP Semiconductors
UM10208
Chapter 17: LPC2800 USB Device
8.12 USB Frame Number Register (USBFN - 0x8004 1074)
This read-only register contains the frame number of the last successfully received SOF.
To ensure correct and consistent values, read 16 or 32 bits from this register rather than
reading bytes.
8.13 USB Scratch Register (USBScratch - 0x8004 1078)
This read/write register can be used by software/firmware to store state information before
entering a low power mode for Suspend state. A Bus Reset does not change bits 15:0.
8.14 USB Unlock Register (USBUnlock - 0x8004 107C)
In Suspend state, all USB registers are write-protected. They remain write protected after
operation is Resumed. Write 0xAA37 to this write-only register to unlock the USB
Controller registers for writing.
Table 242. USB Frame Number Register (USBFN - 0x8004 1074)
Bit
Symbol Description
Master
Reset
value
Bus
Reset
value
10:0
SOF
Frame number
0
0
13:11
mSOF
mSOF number
0
0
31:14 -
Reserved. The values read from reserved bits is not defined.
-
-
Table 243. USB Scratch Register (USBScratch - 0x8004 1078)
Bit
Symbol Description
Master
Reset
value
Bus
Reset
value
15:0
Scratch Information
0
NC
31:16 -
Reserved, software should not write ones to reserved bits. The
values read from reserved bits is not defined.
-
-
Table 244. USB Unlock Register (USBUnlock - 0x8004 107C)
Bit
Symbol
Description
15:0
UnlockCode
Write the value 0xAA37 to this field after Suspend and Resume, to allow
writing to the USB Controller registers and FIFOs.
31:16 -
Reserved, software should not write ones to reserved bits.