
The following table shows how the data direction corresponds to the USB token type in
host and peripheral device applications.
Table 43-1. Data direction for USB host or USB peripheral device
RX
TX
Device
OUT or SETUP
IN
Host
IN
OUT or SETUP
43.3.3 Addressing BDT entries
An understanding of the addressing mechanism of the Buffer Descriptor Table is useful
when accessing endpoint data via USBFS or microprocessor. Some points of interest are:
• The BDT occupies up to 512 bytes of system memory.
• 16 bidirectional endpoints can be supported with a full BDT of 512 bytes.
• 16 bytes are needed for each USB endpoint direction.
• Applications with fewer than 16 endpoints require less RAM to implement the BDT.
• The BDT Page Registers (BDT_PAGE) point to the starting location of the BDT.
• The BDT must be located on a 512-byte boundary in system memory.
• All enabled TX and RX endpoint BD entries are indexed into the BDT to allow easy
access via USBFS or MCU core.
When a USB token on an enabled endpoint is received, USBFS uses its integrated DMA
controller to interrogate the BDT. USBFS reads the corresponding endpoint BD entry to
determine whether it owns the BD and corresponding buffer in system memory.
To compute the entry point into the BDT, the BDT_PAGE registers are concatenated
with the current endpoint and the TX and ODD fields to form a 32-bit address. This
address mechanism is shown in the following tables:
Table 43-2. BDT Address Calculation
31:24
23:16
15:9
8:5
4
3
2:0
BDT_PAGE_03
BDT_PAGE_02
BDT_PAGE_01[7:1]
Endpoint
TX
ODD
000
Table 43-3. BDT address calculation fields
Field
Description
BDT_PAGE
BDT_PAGE registers in the Control Register Block
ENDPOINT
ENDPOINT field from the USB TOKEN
TX
1 for transmit transfers and 0 for receive transfers
Table continues on the next page...
Chapter 43 Universal Serial Bus Full Speed OTG Controller (USBFSOTG)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors
1077
Содержание K22F series
Страница 2: ...K22F Sub Family Reference Manual Rev 4 08 2016 2 NXP Semiconductors...
Страница 150: ...Private Peripheral Bus PPB memory map K22F Sub Family Reference Manual Rev 4 08 2016 150 NXP Semiconductors...
Страница 168: ...Module clocks K22F Sub Family Reference Manual Rev 4 08 2016 168 NXP Semiconductors...
Страница 198: ...Security Interactions with other Modules K22F Sub Family Reference Manual Rev 4 08 2016 198 NXP Semiconductors...
Страница 258: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 258 NXP Semiconductors...
Страница 292: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 292 NXP Semiconductors...
Страница 398: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 398 NXP Semiconductors...
Страница 628: ...Initialization and application information K22F Sub Family Reference Manual Rev 4 08 2016 628 NXP Semiconductors...
Страница 740: ...Initialization Application Information K22F Sub Family Reference Manual Rev 4 08 2016 740 NXP Semiconductors...
Страница 750: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 750 NXP Semiconductors...
Страница 816: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 816 NXP Semiconductors...
Страница 866: ...Initialization Application Information K22F Sub Family Reference Manual Rev 4 08 2016 866 NXP Semiconductors...
Страница 890: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 890 NXP Semiconductors...
Страница 1028: ...Initialization Procedure K22F Sub Family Reference Manual Rev 4 08 2016 1028 NXP Semiconductors...
Страница 1040: ...Example configuration for chained timers K22F Sub Family Reference Manual Rev 4 08 2016 1040 NXP Semiconductors...
Страница 1118: ...Device mode IRC48 operation K22F Sub Family Reference Manual Rev 4 08 2016 1118 NXP Semiconductors...
Страница 1122: ...USB Voltage Regulator Module Signal Descriptions K22F Sub Family Reference Manual Rev 4 08 2016 1122 NXP Semiconductors...
Страница 1180: ...Initialization application information K22F Sub Family Reference Manual Rev 4 08 2016 1180 NXP Semiconductors...
Страница 1302: ...Application information K22F Sub Family Reference Manual Rev 4 08 2016 1302 NXP Semiconductors...
Страница 1374: ...Functional description K22F Sub Family Reference Manual Rev 4 08 2016 1374 NXP Semiconductors...