M68EVB908GB60E Freescale Semiconductor, M68EVB908GB60E Datasheet - Page 112

• Manufacturer Part Number: M68EVB908GB60E
• Description: BOARD EVAL FOR MC9S08GB60
• Manufacturer: Freescale Semiconductor
• Type: MCUr

Specifications of M68EVB908GB60E

• Contents: Module and Misc Hardware
• Processor To Be Evaluated: MC9S08GB
• Data Bus Width: 8 bit
• Interface Type: RS-232
• Silicon Manufacturer: Freescale
• Core Architecture: HCS08
• Core Sub-architecture: HCS08
• Silicon Core Number: MC9S08
• Silicon Family Name: S08GB
• Kit Contents: GB60 Evaluation Kit
• Rohs Compliant: Yes
• For Use With/related Products: MC9S08GB60
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Internal Clock Generator (ICG) Module
7.4.2
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
ICGTRM = $xx
Figure 7-8
112
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
Only needed in self-clocked mode; FLT will be adjusted by loop to give 8.38 MHz DCO clock
Bits 15:12 unused
Bits 11:0 FLT
Bits 7:0
shows flow charts for three conditions requiring ICG initialization.
Example #1: External Crystal = 32 kHz, Bus Frequency = 4.19 MHz
RANGE
REFS
OSCSTEN 0
LOLRE
LOCRE
TRIM
N / R = 8.38 MHz /(32 kHz * 64) = 4 ; we can choose N = 4 and R =1
0
0
1
11
0
0
0
000 Sets the MFD multiplication factor to 4
0
000 Sets the RFD division factor to ÷1
0000
No need for user initialization
Only need to write when trimming internal oscillator; not used when external
crystal is clock source
f
ICGOUT
Unimplemented or reserved, always reads zero
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 in stop modes
Reserved for Freescale Semiconductor internal use; always write zero
Unimplemented or reserved, always reads zero
Generates an interrupt request on loss of lock
Generates an interrupt request on loss of clock
= f
ext
MC9S08GB/GT Data Sheet, Rev. 2.3
* P * N / R ; P = 64, f
ext
= 32 kHz
Bus
).
Freescale Semiconductor
Eqn. 7-1
Eqn. 7-2