STMicroelectronics STM32F405 Reference Manual page 1336

USB on-the-go full-speed (OTG_FS)
}
}
else
if (STALL or FRMOR or NAK or DTERR or BBERR)
{
Mask ACK
Unmask CHH
Disable Channel
if (STALL or BBERR)
else
}
else
if (TXERR)
{
Increment Error Count
Unmask ACK
Unmask CHH
Disable Channel
}
else
if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
else
}
}
else
if (ACK)
{
Reset Error Count
Mask ACK
1336/1731
{
Reset Error Count
Transfer Done = 1
}
if (!FRMOR)
{
Reset Error Count
}
{
De-allocate Channel
}
Re-initialize Channel (in next b_interval - 1 /Frame)
DocID018909 Rev 11
RM0090