mc9s08ac32 Freescale Semiconductor, Inc, mc9s08ac32 Datasheet - Page 182

• Manufacturer Part Number: mc9s08ac32
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 10 Internal Clock Generator (S08ICGV4)
10.6.2
In this example, the FLL will be used (in FEE mode) to multiply the external 32 kHz oscillator up to
8.38 MHz to achieve 4.19 MHz bus frequency.
After the MCU is released from reset, the ICG is in self-clocked mode (SCM) and supplies approximately
8 MHz on ICGOUT, which corresponds to a 4 MHz bus frequency (f
The clock scheme will be FLL engaged, external (FEE). So
Solving for N / R gives:
The values needed in each register to set up the desired operation are:
ICGC1 = $38 (%00111000)
ICGC2 = $00 (%00000000)
ICGS1 = $xx
ICGS2 = $xx
ICGFLTLU/L = $xx
182
Bit 7
Bit 6
Bit 5
Bits 4:3 CLKS
Bit 2
Bit 1
Bit 0
Bit 7
Bits 6:4 MFD
Bit 3
Bits 2:0 RFD
This is read only except for clearing interrupt flag
This is read only; should read DCOS = 1 before performing any time critical tasks
011
100
101
110
111
Example #1: External Crystal = 32 kHz, Bus Frequency = 4.19 MHz
HGO
RANGE
REFS
OSCSTEN 0
LOCD
LOLRE
LOCRE
N / R = 8.38 MHz /(32 kHz * 64) = 4 ; we can choose N = 4 and R =1
f
0
0
1
11
0
0
0
000 Sets the MFD multiplication factor to 4
0
000 Sets the RFD division factor to ÷1
ICGOUT
10
12
14
16
18
Configures oscillator for low power
Configures oscillator for low-frequency range; FLL prescale factor is 64
Oscillator using crystal or resonator is requested
FLL engaged, external reference clock mode
Oscillator disabled
Loss-of-clock detection enabled
Unimplemented or reserved, always reads zero
Generates an interrupt request on loss of lock
Generates an interrupt request on loss of clock
Table 10-12. MFD and RFD Decode Table
= f
ext
MC9S08AC60 Series Data Sheet, Rev. 2
* P * N / R ; P = 64, f
ext
011
100
101
110
111
= 32 kHz
Bus
).
Freescale Semiconductor
÷128
÷16
÷32
÷64
÷8
Eqn. 10-1
Eqn. 10-2