Configuring Clocks in PSoC® 4000 - KBA91259

Version: *B

 

Question:

How do you configure the clocks in the PSoC® 4000 device?

 

Answer:

Clock sources in PSoC 4000 are of two types: high frequency and low frequency. High-frequency clock sources include the internal main oscillator (IMO) and external clock (EXTCLK), and their derived clocks – system clock (SYSCLK) and high-frequency clock (HFCLK). Low-frequency clock sources include internal low-speed oscillator (ILO) and its derived clock – low-frequency clock (LFCLK). The clocks are configured in the cydwr file of the PSoC Creator™ project. Open the [ProjectName].cydwr file from the Workspace and click the Clocks tab.

To edit the high-frequency clock, select any high-frequency clock source and click the Edit Clock button. The Configure System Clocks Window shown in Figure 1 will open.

Figure 1. Configure System Clocks Window – High Frequency Clocks

Figure 1. Configure System Clocks Window – High Frequency Clocks

The High Frequency Clocks tab allows you to

  • Enable or disable the IMO and EXTCLK.
  • Select the clock source for the HFCLK as IMO or EXTCLK.
  • Configure the IMO, HFCLK, and SYSCLK frequency.
  • Set the divider for the HFCLK to ‘1’, ‘2’, ‘4’, or ‘8’. 
  • Set the divider for the SYSCLK to ‘1’, ‘2’, ‘4’, or ‘8’.

To edit the low-frequency clock, click the Low Frequency Clocks tab in the Configure System Clocks window. See Figure 2 for reference. 

Figure 2. Configure System Clocks Window - Low Frequency Clocks

Figure 2. Configure System Clocks Window - Low Frequency Clocks

This tab allows you to 

  • Enable or disable the ILO and watchdog timer (WDT) block.
  • Configure the mode of the WDT block as general-purpose free-running timer or as watchdog timer.
  • Set the period of the WDT block.
  • Select between auto-generated interrupt service routine and custom (user) routine. 

For more information on low-frequency clock and WDT configuration, refer to the LFCLK Component datasheet from the System Reference Guide (accessed from the Help menu of PSoC Creator).