Datasheet

Chapter 10 Internal Clock Source (S08ICSV2)
MC9S08SH8 MCU Series Data Sheet, Rev. 3
156 Freescale Semiconductor
10.3.3 ICS Trim Register (ICSTRM)
10.3.4 ICS Status and Control (ICSSC)
7 654 3 210
R
TRIM
W
POR: 1 0 0 0 0 0 0 0
Reset: U U U U U U U U
Figure 10-5. ICS Trim Register (ICSTRM)
Table 10-4. ICS Trim Register Field Descriptions
Field Description
7:0
TRIM
ICS Trim Setting — The TRIM bits control the internal reference clock frequency by controlling the internal
reference clock period. The bits’ effect are binary weighted (i.e., bit 1 will adjust twice as much as bit 0).
Increasing the binary value in TRIM will increase the period, and decreasing the value will decrease the period.
An additional fine trim bit is available in ICSSC as the FTRIM bit.
7 654 3 210
R 0 0 0 IREFST CLKST OSCINIT
FTRIM
W
POR:
Reset:
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
U
Figure 10-6. ICS Status and Control Register (ICSSC)
Table 10-5. ICS Status and Control Register Field Descriptions
Field Description
7:5 Reserved, should be cleared.
4
IREFST
Internal Reference Status — The IREFST bit indicates the current source for the reference clock. The IREFST
bit does not update immediately after a write to the IREFS bit due to internal synchronization between clock
domains.
0 Source of reference clock is external clock.
1 Source of reference clock is internal clock.
3-2
CLKST
Clock Mode Status — The CLKST bits indicate the current clock mode. The CLKST bits don’t update
immediately after a write to the CLKS bits due to internal synchronization between clock domains.
00 Output of FLL is selected.
01 FLL Bypassed, Internal reference clock is selected.
10 FLL Bypassed, External reference clock is selected.
11 Reserved.