In Device mode, this register is valid only in Shared FIFO operation. It contains the free space information for the Non-periodic TxFIFO and the Nonperiodic Transmit RequestQueue
Module Instance Base Address Register Address
usb0 0xFFB00000 0xFFB0002C
usb1 0xFFB40000 0xFFB4002C

Offset: 0x2C

Access: RO

Important: To prevent indeterminate system behavior, reserved areas of memory must not be accessed by software or hardware. Any area of the memory map that is not explicitly defined as a register space or accessible memory is considered reserved.
Bit Fields
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16



RO 0x0


RO 0x8

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0


RO 0x400

gnptxsts Fields

Bit Name Description Access Reset
30:24 nptxqtop

Entry in the Non-periodic Tx Request Queue that is currently being processed by the MAC. -Bits [30:27]: Channel/endpoint number -Bits [26:25]: -Bit [24]: Terminate (last Entry for selected channel endpoint)

Value Description
0x0 IN/OUT token
0x1 Zero-length transmit packet (device IN/host OUT)
0x2 PING/CSPLIT token
0x3 Channel halt command
RO 0x0
23:16 nptxqspcavail

Indicates the amount of free space available in the Non-periodic Transmit Request Queue. This queue holds both IN and OUT requests in Host mode. Device mode has only IN requests. -Others: Reserved

Value Description
0x0 Non-periodic Transmit Request Queue is full
0x1 1 location available
0x2 2 locations available
0x3 3 locations available
0x4 4 locations available
0x5 5 locations available
0x6 6 locations available
0x7 7 locations available
0x8 8 locations available
RO 0x8
15:0 nptxfspcavail

Indicates the amount of free space available in the Non-periodic TxFIFO.Values are in terms of 32-bit words. 16h0: Non-periodic TxFIFO is full 16h1: 1 word available 16h2: 2 words available 16hn: n words available (where 0 n 32,768) 16h8000: 32,768 words available Others: Reserved

RO 0x400