Motorola SC140 5Setting Up the System Clock Speed

12 Using the SC140 Enhanced OnCE Stopwatch Timer 

Figure 7. Event Counter Dialog Box When Debugger Halts at Breakpoint

5Setting Up the System Clock Speed

Every SC140-based device contains a Phase Lock Loop (PLL) block, which controls the operating

frequency of the device. The frequency of the device is governed by the frequency control bits in the PLL

control register, as defined in Equation2.

Eqn. 2

In this equation:

•MFI (multiplication factor integer), MFN (multiplication factor numerator), MFD (multiplication

factor denominator), and PODF (post division factor) are defined in the PCTL1 register.

•PDF (pre-division factor) is defined in the P CTL0 register.

•Fext is external input frequency to the chip at the EXTAL pin.

•Fdevice is the operating frequency of the device.

The range of values of these terms are describe in [1].

Figure 8 and Figure9 on page -13 illustrate the PLL control registers; PCTL0 and PCTL1, respectively.

Fdevice

Fext MFI MFN

MFD

-------------

+





×

PODF PDF×

-------------------------------------------------------

=

Contents

Main Page Abstract and Contents Page 1Introduction 2SC140 Enhanced OnCE Stopwatch Timer Capabilities 2.1 Features 2.2 Resources 2.3 Implementation 3Setting Up the Stopwatch Timer Within an Application 3.1 Initializing the Stopwatch Timer 3.1.1 Event Detector Control 3.1.2 Address Comparison Setup 3.2 Starting the Stopwatch Timer 3.2.1 Event Counter Control 3.2.2 Counter Registers 3.3 Stopping the Stopwatch Timer Time ms() EXT 0xffffffffVAL+() 3.4 Converting Cycles to Actual Time 1000 ClockSpeed -------------------------------- = 3.5 Putting it All Together modules as desired. Code 5 depicts the use of the stopwatch timer using the routines that have been described so far. 3.6 Adapting Stopwatch Timer Code to Other SC140 Devices 4Setting Up the Stopwatch Timer Within the Debugger 4.1 Initializing the Stopwatch Timer 4.1.1 Setting Up the Event Detector Page 4.1.2 Setting Up the Event Counter 4.2 Stopping the Stopwatch Timer 5Setting Up the System Clock Speed 5.1 Setting Up the PLL in Software 5.2 Setting Up the PLL in Hardware 6Verifying Correct Setup 6.1 Using the LED on the SDP 6.1.1 Setting Up EE1 6.1.2 Toggling EE1 6.2 Testing the Stopwatch Timer 16 Using the SC140 Enhanced OnCE Stopwatch Timer Code 9. Testing Code 7Conclusion 8References Page Appendix A Complete Example of Profiling Code A-1. EOnCE_stopwatch.h A-2 Using the SC140 Enhanced OnCE Stopwatch Timer Code A-2. EOnCE_registers.h Code A-3. EOnCE_stopwatch.c A-4 Using the SC140 Enhanced OnCE Stopwatch Timer Code A-4. autocorr.c