NXP Semiconductors MC9S08QL4, Reference Manual

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Internal Clock Source (S08ICSV3)
MC9S08QL8 MCU Series Reference Manual, Rev. 1
NXP Semiconductors 153
11.3.1 ICS Control Register 1 (ICSC1)
ICSSC
R DRST
DMX32
IREFST CLKST OSCINIT
FTRIM
W DRS
7 6 5 4 3 2 1 0
R
CLKS RDIV IREFS IRCLKEN IREFSTEN
W
Reset: 0 0 0 0 0 1 0 0
Figure 11-2. ICS Control Register 1 (ICSC1)
Table 11-2. ICS Control Register 1 Field Descriptions
Field Description
7:6
CLKS
Clock Source Select — Selects the clock source that controls the bus frequency. The actual bus frequency
depends on the value of the BDIV bits.
00
Output of FLL is selected.
01 Internal reference clock is selected.
10 External reference clock is selected.
11 Reserved, defaults to 00.
5:3
RDIV
Reference Divider — Selects the amount to divide down the external reference clock. Resulting frequency must
be in the range 31.25 kHz to 39.0625 kHz. See Table 11-3 for the divide-by factors.
2
IREFS
Internal Reference Select — The IREFS bit selects the reference clock source for the FLL.
1 Internal reference clock selected.
0 External reference clock selected.
1
IRCLKEN
Internal Reference Clock Enable — The IRCLKEN bit enables the internal reference clock for use as
ICSIRCLK.
1 ICSIRCLK active.
0 ICSIRCLK inactive.
0
IREFSTEN
Internal Reference Stop Enable — The IREFSTEN bit controls whether or not the internal reference clock
remains enabled when the ICS enters stop mode.
1 Internal reference clock stays enabled in stop if IRCLKEN is set before entering stop.
0 Internal reference clock is disabled in stop.
Table 11-3. Reference Divide Factor
RDIV RANGE=0 RANGE=1
0
1
1
32
1 2 64
2 4 128
3 8 256
Table 11-1. ICS Register Summary (continued)
Name
7 6 5 4 3 2 1 0