SAMD21 Generic Clock Controller (GCLK) Overview

Depending on the application, peripherals may require specific clock frequencies to operate correctly. The Generic Clock Controller (GCLK) provides eight Generic Clock Generators that can provide a wide range of clock frequencies.

One or more master source clocks can be selected as the input clock to a Generic Clock Generator. A clock source selected as input to a generator can either be used directly, or it can be prescaled in the generator. The outputs from the generators are used as sources for the Generic Clock Multiplexers, which provide the Generic Clock (GCLK_PERIPHERAL) to the peripheral modules, as shown in the Generic Clock Controller Block Diagram below. The number of Peripheral Clocks depends on how many peripherals the device has.

Generator 0 is always the direct source of the GCLK_MAIN signal.

GCLKBlockDiagram.png

Generic Clock Generators

Each Generic Clock Generator within the device can source its input clock from one of the provided source clocks and prescale the output for one or more Generic Clock Channels in a one-to-many relationship. The generators thus allow for several clocks to be generated with different frequencies, power usages, and accuracies, which can be turned on and off individually to disable the clocks to multiple peripherals as a group.

Generic Clock Channels

A Generic Clock Channel is used to connect a Generic Clock Generator to a peripheral within the device. Each peripheral or peripheral group has an associated Generic Clock Channel, which serves as the clock input for the peripheral(s). To supply a clock to the peripheral module(s), the associated channel must be connected to a running Generic Clock Generator and the channel enabled.

© 2018 Microchip Technology, Inc.
Notice: ARM and Cortex are the registered trademarks of ARM Limited in the EU and other countries.
Information contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights.