RM0090: Reference manual - STMicroelectronics

USB on-the-go high-speed (OTG_HS) RM0090
Bit 0 CSRST: Core soft reset
Resets the HCLK and PCLK domains as follows:
Clears the interrupts and all the CSR register bits except for the following bits:
– RSTPDMODL bit in OTG_HS_PCGCCTL
– GAYEHCLK bit in OTG_HS_PCGCCTL
– PWRCLMP bit in OTG_HS_PCGCCTL
– STPPCLK bit in OTG_HS_PCGCCTL
– FSLSPCS bit in OTG_HS_HCFG
– DSPD bit in OTG_HS_DCFG
All module state machines (except for the AHB slave unit) are reset to the Idle state, and all
the transmit FIFOs and the receive FIFO are flushed.
Any transactions on the AHB Master are terminated as soon as possible, after completing the
last data phase of an AHB transfer. Any transactions on the USB are terminated immediately.
The application can write to this bit any time it wants to reset the core. This is a self-clearing bit
and the core clears this bit after all the necessary logic is reset in the core, which can take
several clocks, depending on the current state of the core. Once this bit has been cleared, the
software must wait at least 3 PHY clocks before accessing the PHY domain (synchronization
delay). The software must also check that bit 31 in this register is set to 1 (AHB Master is Idle)
before starting any operation.
Typically, the software reset is used during software development and also when you
dynamically change the PHY selection bits in the above listed USB configuration registers.
When you change the PHY, the corresponding clock for the PHY is selected and used in the
PHY domain. Once a new clock is selected, the PHY domain has to be reset for proper
operation.
Note: Accessible in both peripheral and host modes.
1189/1416 Doc ID 018909 Rev 3