Datasheet

Table 2. Buffer descriptor format (continued)

TOK_PID[

Buffer Address(32-Bits)

The address of the EP Buffer is stored in the Buffer Address field. BDT is stored in a 512 byte aligned space and the location of

the BDT can be determined by BDT Page registers: BDT Page register 1, BDT Page register 2 and BDT Page register 3. These

three registers provide bit 9 -bit 31 bits of the BDT address, where bit 0-bit 8 is 0, as shown in Table 3.

Table 3. BDT Address

BDT Page

BDT Page register 1

BDT

address

bit 31— bit

bit 23 — bit

bit 15 — bit 9 0 0 0 0 0 0 0 0 0

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 Table 4.

Table 4. BDT Address Calculation

31:24 23:16 15:9 8:5 4 3 2

BDT_PAGE_03 BDT_PAGE_02 BDT_PAGE_01[

7:1]

Endpoint TX ODD 000

Table 5. BDT address calculation fields

Field Description

BDT_PAGE BDT_PAGE register in the Control Register Block

ENDPOINT ENDPOINT field from the USB TOKEN

TX 1 for transmit transfers and 0 for receive transfers

ODD Maintained within the USBFS SIE. It corresponds to the buffer currently in

use. The buffers are used in a ping-pong fashion.

According to the values of several fields in Table 4, you can find the corresponding BD in BDT and the corresponding EP Buffer,

as shown in Figure 3.

NXP Semiconductors

Endpoint Buffer Configuration

USB to Multi VCOM on K32L2 Series MCU, Rev. 0, November 2019

Application Note 5 / 25