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Software must ensure that the reset is active for a minimum of two
usb_mp_c lk
cycles. There is no
maximum assertion time.
Hardware Reset
Each of the USB OTG controllers has one reset input from the reset manager. The reset signal is asserted
during a cold or warm reset event. The reset manager holds the controllers in reset until software releases
the resets. Software releases resets by clearing the appropriate USB bits in the Peripheral Module Reset
Register (
permodrst
) in the HPS reset manager.
The reset input resets the following blocks:
• The master and slave interface logic
• The integrated DMA controller
• The internal FIFO buffers
• The CSR
The reset input is synchronized to the
usb_mp_clk
domain. The reset input is also synchronized to the
ULPI clock within the USB OTG controller and is used to reset the ULPI PHY domain logic.
Software Reset
Software can reset the controller by setting the Core Soft Reset (
csftrst
) bit in the Reset Register
(
grstctl
) in the Global Registers (
globgrp
) group of the USB OTG controller.
Software resets are useful in the following situations:
• A PHY selection bit is changed by software. Resetting the USB OTG controller is part of clean-up to
ensure that the PHY can operate with the new configuration or clock.
• During software development and debugging.
Interrupts
Table 18-4: USB OTG Interrupt Conditions
Each USB OTG controller has a single interrupt output. Interrupts are asserted on the conditions shown in the
following table.
Mode
Condition
Host mode
Device-initiated remote wakeup is detected.
Host mode
Session request is detected from the device.
Host mode
Device disconnect is detected.
Host mode
Host LPM entry retry has expired or LPM transaction(s) are complete.
Host mode
Host periodic TX FIFO buffer is empty (can be further programmed to
indicate half-empty).
Host mode
Host channels interrupt received.
Host mode
Incomplete periodic transfer is pending at the end of the microframe.
Host mode
Host port status interrupt received.
USB 2.0 OTG Controller
Altera Corporation
cv_54018
Hardware Reset
18-10
2013.12.30