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DocID024597 Rev 3 1553/1693

RM0351 USB on-the-go full-speed (OTG_FS)

1644

43.15.22 OTG Host frame number/frame time remaining register

(OTG_HFNUM)

Address offset: 0x408

Reset value: 0x0000 3FFF

This register indicates the current frame number. It also indicates the time remaining (in

terms of the number of PHY clocks) in the current frame.

Bits 31:17 Reserved, must be kept at reset value.

Bit 16 RLDCTRL: Reload control

This bit allows dynamic reloading of the HFIR register during run time.

0: The HFIR cannot be reloaded dynamically

1: The HFIR can be dynamically reloaded during runtime.

This bit needs to be programmed during initial configuration and its value must not be

changed during runtime.

Bits 15:0 FRIVL: Frame interval for USB OTG FS

The value that the application programs to this field, specifies the interval between two

consecutive SOFs (FS) or Keep-Alive tokens (LS). This field contains the number of PHY

clocks that constitute the required frame interval. The application can write a value to this

OTG_HPRT) has been set. If no value is programmed, the core calculates the value based

on the PHY clock specified in the FS/LS PHY Clock Select field of the host configuration

configuration, unless the RLDCTRL bit is set. In such case, the FRIVL is reloaded with each

SOF event.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

FTREM

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FRNUM

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Bits 31:16 FTREM: Frame time remaining

Indicates the amount of time remaining in the current frame, in terms of PHY clocks. This

field decrements on each PHY clock. When it reaches zero, this field is reloaded with the

value in the Frame interval register and a new SOF is transmitted on the USB.

Bits 15:0 FRNUM: Frame number

This field increments when a new SOF is transmitted on the USB, and is cleared to 0 when

it reaches 0x3FFF.

ST STM32L4x6 User Manual

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