AN2090 Freescale Semiconductor / Motorola, AN2090 Datasheet - Page 12

• Manufacturer Part Number: AN2090
• Description: Using the SC140/SC1400 Enhanced On-Chip Emulator Stopwatch Timer
• Manufacturer: Freescale Semiconductor / Motorola

Setting Up the System Clock Speed
4
Every SC140-based device contains a phase lock loop (PLL) to control operating frequency. The frequency of the
device is governed by the frequency control bits in the PLL control register, as defined in Equation 2.
Where:
The range of values of these terms is described in [1].
Figure 8 and Figure 9 illustrate the PLL registers; PCTL0 and PCTL1, respectively.
12
Setting Up the System Clock Speed
•
•
•
•
MFI (multiplication factor integer), MFN (multiplication factor numerator), MFD (multiplication
factor denominator), and PODF (post division factor) are defined in the PCTL1 register.
PDF (predivision factor) is defined in the PCTL0 register.
F
F
ext
device
is external input frequency to the device at the
Using the SC140/SC1400 Enhanced On-Chip Emulator Stopwatch Timer, Rev. 1
is the device operating frequency.
Figure 7. Event Counter Dialog Box When Debugger Halts at Breakpoint
Fdevice
=
Fext
------------------------------------------------------- -
PODF
×
⎛
⎝
MFI
×
PDF
+
MFN
------------ -
MFD
EXTAL
⎞
⎠
pin.
Freescale Semiconductor
Equation 2