Clock recovery is achieved by a digital phase-locked loop in the USB module, which complies with the
USB jitter specifications. If crystal-less operation is used in USB device mode, refer to
USB Clock
Recovery Module
.
Related Links
GCLK - Generic Clock Controller
on page 121
39.5.4. DMA
The USB has a built-in Direct Memory Access (DMA) and will read/write data to/from the system RAM
when a USB transaction takes place. No CPU or DMA Controller resources are required.
39.5.5. Interrupts
The interrupt request line is connected to the Interrupt Controller. In order to use interrupt requests of this
peripheral, the Interrupt Controller (NVIC) must be configured first. Refer to
Nested Vector Interrupt
Controller
for details.
Related Links
Nested Vector Interrupt Controller
on page 44
39.5.6. Events
Not applicable.
39.5.7. Debug Operation
When the CPU is halted in debug mode the USB peripheral continues normal operation. If the USB
peripheral is configured in a way that requires it to be periodically serviced by the CPU through interrupts
or similar, improper operation or data loss may result during debugging.
39.5.8. Register Access Protection
Registers with write-access can be optionally write-protected by the Peripheral Access Controller (PAC),
except the following:
•
Device Interrupt Flag (INTFLAG) register
•
Endpoint Interrupt Flag (EPINTFLAG) register
Note:
Optional write-protection is indicated by the "PAC Write-Protection" property in the register
description.
When the CPU is halted in debug mode, all write-protection is automatically disabled. Write-protection
does not apply for accesses through an external debugger.
39.5.9. Analog Connections
Not applicable.
39.5.10. Calibration
The output drivers for the DP/DM USB line interface can be fine tuned with calibration values from
production tests. The calibration values must be loaded from the NVM Software Calibration Area into the
USB Pad Calibration register (PADCAL) by software, before enabling the USB, to achieve the specified
accuracy. Refer to
NVM Software Calibration Area Mapping
for further details.
For details on Pad Calibration, refer to Pad Calibration (
Related Links
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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