Table 33-5. Buffer descriptor fields (continued)
Field
Description
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.
1–0
Reserved
Reserved, should read as zeroes.
ADDR[31:0]
Address
Represents the 32-bit buffer address in system memory. These bits are unchanged by USBFS.
33.4.5 USB transaction
When USBFS transmits or receives data, it computes the BDT address using the address
generation shown in "Addressing Buffer Descriptor Entries" table.
If OWN =1, the following process occurs:
1. USBFS reads the BDT.
2. The SIE transfers the data via the DMA to or from the buffer pointed to by the
ADDR field of the BD.
3. When the TOKEN is complete, USBFS updates the BDT and, if KEEP=0, changes
the OWN bit to 0.
4. The STAT register is updated and the TOK_DNE interrupt is set.
5. When the processor processes the TOK_DNE interrupt, it reads from the status
register all the information needed to process the endpoint.
6. At this point, the processor allocates a new BD so that additional USB data can be
transmitted or received for that endpoint, and then processes the last BD.
The following figure shows a timeline of how a typical USB token is processed after the
BDT is read and OWN=1.
Chapter 33 Universal Serial Bus (USB) FS Subsystem
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
539
Содержание MKL27Z128VFM4
Страница 2: ...KL27 Sub Family Reference Manual Rev 5 01 2016 2 Freescale Semiconductor Inc...
Страница 54: ...AWIC introduction KL27 Sub Family Reference Manual Rev 5 01 2016 54 Freescale Semiconductor Inc...
Страница 100: ...Module operation in low power modes KL27 Sub Family Reference Manual Rev 5 01 2016 100 Freescale Semiconductor Inc...
Страница 142: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 142 Freescale Semiconductor Inc...
Страница 248: ...Memory map and register descriptions KL27 Sub Family Reference Manual Rev 5 01 2016 248 Freescale Semiconductor Inc...
Страница 256: ...Memory map register descriptions KL27 Sub Family Reference Manual Rev 5 01 2016 256 Freescale Semiconductor Inc...
Страница 262: ...Initialization application information KL27 Sub Family Reference Manual Rev 5 01 2016 262 Freescale Semiconductor Inc...
Страница 292: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 292 Freescale Semiconductor Inc...
Страница 324: ...Functional Description KL27 Sub Family Reference Manual Rev 5 01 2016 324 Freescale Semiconductor Inc...
Страница 390: ...Application information KL27 Sub Family Reference Manual Rev 5 01 2016 390 Freescale Semiconductor Inc...
Страница 422: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 422 Freescale Semiconductor Inc...
Страница 432: ...Initialization Application Information KL27 Sub Family Reference Manual Rev 5 01 2016 432 Freescale Semiconductor Inc...
Страница 442: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 442 Freescale Semiconductor Inc...
Страница 512: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 512 Freescale Semiconductor Inc...
Страница 610: ...Initialization application information KL27 Sub Family Reference Manual Rev 5 01 2016 610 Freescale Semiconductor Inc...
Страница 646: ...Initialization application information KL27 Sub Family Reference Manual Rev 5 01 2016 646 Freescale Semiconductor Inc...
Страница 744: ...Application information KL27 Sub Family Reference Manual Rev 5 01 2016 744 Freescale Semiconductor Inc...
Страница 784: ...Application Information KL27 Sub Family Reference Manual Rev 5 01 2016 784 Freescale Semiconductor Inc...
Страница 830: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 830 Freescale Semiconductor Inc...
Страница 850: ...Application information KL27 Sub Family Reference Manual Rev 5 01 2016 850 Freescale Semiconductor Inc...
Страница 886: ...Functional description KL27 Sub Family Reference Manual Rev 5 01 2016 886 Freescale Semiconductor Inc...