ST STM32F446 Series Reference Manual page 1218

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
if (XFRC)
{
Reset Error Count
Mask ACK
De-allocate Channel
}
else
if (STALL or FRMOR)
{
Mask ACK
Unmask CHH
Disable Channel
if (STALL)
}
else
if (NAK or TXERR)
else
else
1218/1328
{
Transfer Done = 1
}
{
Rewind Buffer Pointers
Reset Error Count
Mask ACK
Unmask CHH
Disable Channel
}
if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
{
Re-initialize Channel (in next b_interval - 1 Frame)
}
}
if (ACK)
{
Reset Error Count
Mask ACK
}
RM0390 Rev 4
RM0390