Information

ManualsBrandsNXP SEMICONDUCTORS ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller LQFP 80 (12x12) 32-Bit 100 MHz I/O number 52

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USBx_TOKEN field descriptions

Field Description

7–4

TOKENPID

This 4-bit field contains the token type executed by the USB Module.

0001 OUT Token. USB Module performs an OUT (TX) transaction.

1001 IN Token. USB Module performs an In (RX) transaction.

1101 SETUP Token. USB Module performs a SETUP (TX) transaction

3–0

TOKENENDPT

This 4 bit field holds the Endpoint address for the token command. The four bit value written must be a

valid endpoint.

42.4.20 SOF Threshold Register (USBx_SOFTHLD)

The SOF Threshold Register is used only in Hosts mode (HOSTMODEEN=1). When in

Host mode, the 14-bit SOF counter counts the interval between SOF frames. The SOF

must be transmitted every 1msec so the SOF counter is loaded with a value of 12000.

When the SOF counter reaches zero, a Start Of Frame (SOF) token is transmitted. The

SOF threshold register is used to program the number of USB byte times before the SOF

to stop initiating token packet transactions. This register must be set to a value that

ensures that other packets are not actively being transmitted when the SOF time counts to

zero. When the SOF counter reaches the threshold value, no more tokens are transmitted

until after the SOF ha been transmitted. The value programmed into the threshold register

must reserve enough time to ensure the worst case transaction completes. In general the

worst case transaction is a IN token followed by a data packet from the target followed by

the response from the host. The actual time required is a function of the maximum packet

size on the bus. Typical values for the SOF threshold are: 64-byte packets=74; 32-byte

packets=42; 16-byte packets=26; 8-byte packets=18.

Addresses: USB0_SOFTHLD is 4007_2000h base + ACh offset = 4007_20ACh

Bit 7 6 5 4 3 2 1 0

Read

CNT

Write

Reset

0 0 0 0 0 0 0 0

USBx_SOFTHLD field descriptions

Field Description

7–0

CNT

This 8-bit field represents the SOF count threshold in byte times.

Chapter 42 Universal Serial Bus OTG Controller (USBOTG)

K20 Sub-Family Reference Manual, Rev. 6, Nov 2011

Freescale Semiconductor, Inc. 1075