NXP Semiconductors K32 L2A Series, Reference Manual, Page: 1302 / 1379

Table 51-5. Buffer descriptor fields (continued)
Field Description
3
DTS/
TOK_PID[1]
Setting this bit enables USBFS to perform Data Toggle Synchronization.
• If KEEP=0, bit 1 of the current token PID is written back to the BD.
• If KEEP=1, this bit is unchanged by USBFS.
0 Data Toggle Synchronization is disabled.
1 Enables USBFS to perform Data Toggle Synchronization.
2
BDT_STALL
TOK_PID[0]
Setting this bit causes USBFS to issue a STALL handshake if a token is received by the SIE that
would use the BDT in this location. The BDT is not consumed by the SIE (the owns bit remains set
and the rest of the BDT is unchanged) when a BDT_STALL bit is set.
• If KEEP=0, bit 0 of the current token PID is written back to the BD.
• If KEEP=1, this bit is unchanged by USBFS.
0 No stall issued.
1 The BDT is not consumed by the SIE (the OWN bit remains set and the rest of the BDT is
unchanged).
Setting BDT_STALL also causes the corresponding USB_ENDPT n [EPSTALL] bit to set. This
causes USBOTG to issue a STALL handshake for both directions of the associated endpoint. To
clear the stall condition:
1. Clear the associated USB_ENDPT n [EPSTALL] bit.
2. Write the BDT to clear OWN and BDT_STALL.
TOK_PID[n] Bits [5:2] can also represent the current token PID. The current token PID is written back in to the
BD by USBFS when a transfer completes. The values written back are the token PID values from
the USB specification:
• 0x1h for an OUT token.
• 0x9h for an IN token.
• 0xDh for a SETUP token.
In host mode, this field is used to report the last returned PID or a transfer status indication. The
possible values returned are:
• 0x3h DATA0
• 0xBh DATA1
• 0x2h ACK
• 0xEh STALL
• 0xAh NAK
• 0x0h Bus Timeout
• 0xFh Data Error
1–0
Reserved
Reserved, should read as zeroes.
ADDR[31:0] Address
Represents the 32-bit buffer address in system memory; this address must also be 32-bit aligned.
These bits are unchanged by USBFS.
51.3.5 USB transaction
When USBFS transmits or receives data, it computes the BDT address using the address
generation shown in "Addressing Buffer Descriptor Entries" table.
Programmers interface
K32 L2A Reference Manual, Rev. 2, 01/2020
1302 NXP Semiconductors