39.17.2 Host Start-of-Frame Control

During a very short period just before transmitting a Start-of-Frame, this register is locked. Thus, after writing, it is recommended to check the register value, and write this register again if necessary. This register is cleared upon a USB reset.
Name: HSOFC
Offset: 0x0A
Reset: 0x00
Property: PAC Write-Protection

Bit 76543210 
 FLENCE   FLENC[3:0] 
Access R/WR/WR/WR/WR/W 
Reset 00000 

Bit 7 – FLENCE Frame Length Control Enable

When this bit is '1', the time between Start-of-Frames can be tuned by up to +/-0.06% using FLENC[3:0].
Note: In Low Speed mode, FLENCE must be '0'.
ValueDescription
0 Start-of-Frame is generated every 1ms.
1 Start-of-Frame generation depends on the signed value of FLENC[3:0].

USB Start-of-Frame period equals 1ms + (FLENC[3:0]/12000)ms

Bits 3:0 – FLENC[3:0] Frame Length Control

These bits define the signed value of the 4-bit FLENC that is added to the Internal Frame Length when FLENCE is '1'. The internal Frame length is the top value of the frame counter when FLENCE is zero.