RM0090: Reference manual - STMicroelectronics

USB on-the-go full-speed (OTG_FS) RM0090
Bits 1:0 FSLSPCS: FS/LS PHY clock select
When the core is in FS host mode
01: PHY clock is running at 48 MHz
Others: Reserved
When the core is in LS host mode
00: Reserved
01: Select 48 MHz PHY clock frequency
10: Select 6 MHz PHY clock frequency
11: Reserved
Note: The FSLSPCS must be set on a connection event according to the speed of the
connected device (after changing this bit, a software reset must be performed).
OTG_FS Host frame interval register (OTG_FS_HFIR)
Address offset: 0x404
Reset value: 0x0000 EA60
This register stores the frame interval information for the current speed to which the
OTG_FS controller has enumerated.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
Bits 31:16 Reserved, must be kept at reset value.
1069/1416 Doc ID 018909 Rev 3
FRIVL
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bits 15:0 FRIVL: Frame interval
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
register only after the Port enable bit of the host port control and status register (PENA bit in
OTG_FS_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 register (FSLSPCS in OTG_FS_HCFG). Do not change the value of this field
after the initial configuration.
1 ms × (PHY clock frequency)