Datasheet

S12 Clock, Reset and Power Management Unit (S12CPMU)
MC9S12G Family Reference Manual, Rev.1.23
Freescale Semiconductor 397
10.3.2.18 S12CPMU IRC1M Trim Registers (CPMUIRCTRIMH / CPMUIRCTRIML)
Read: Anytime
Write: Anytime if PROT=0 (CPMUPROT register). Else write has no effect
NOTE
Writes to these registers while PLLSEL=1 clears the LOCK and UPOSC
status bits.
0x02F8
15 14 13 12 11 10 9 8
R
TCTRIM[4:0]
0
IRCTRIM[9:8]
W
Reset F F F F 0 0 F F
After de-assert of System Reset a factory programmed trim value is automatically loaded from the Flash memory to
provide trimmed Internal Reference Frequency f
IRC1M_TRIM
.
Figure 10-23. S12CPMU IRC1M Trim High Register (CPMUIRCTRIMH)
0x02F9
76543210
R
IRCTRIM[7:0]
W
Reset F F FFFFFF
After de-assert of System Reset a factory programmed trim value is automatically loaded from the Flash memory to
provide trimmed Internal Reference Frequency f
IRC1M_TRIM
.
Figure 10-24. S12CPMU IRC1M Trim Low Register (CPMUIRCTRIML)
Table 10-22. CPMUIRCTRIMH/L Field Descriptions
Field Description
15-11
TCTRIM[4:0]
IRC1M temperature coefficient Trim Bits
Trim bits for the Temperature Coefficient (TC) of the IRC1M frequency.
Figure 10-26 shows the influence of the bits TCTRIM4:0] on the relationship between frequency and
temperature.
Figure 10-26 shows an approximate TC variation, relative to the nominal TC of the IRC1M (i.e. for
TCTRIM[4:0]=0b00000 or 0b10000).
9-0
IRCTRIM[9:0]
IRC1M Frequency Trim Bits — Trim bits for Internal Reference Clock
After System Reset the factory programmed trim value is automatically loaded into these registers, resulting in a
Internal Reference Frequency f
IRC1M_TRIM
. See device electrical characteristics for value of f
IRC1M_TRIM
.
The frequency trimming consists of two different trimming methods:
A rough trimming controlled by bits IRCTRIM[9:6] can be done with frequency leaps of about 6% in average.
A fine trimming controlled by the bits IRCTRIM[5:0] can be done with frequency leaps of about 0.3% (this
trimming determines the precision of the frequency setting of 0.15%, i.e. 0.3% is the distance between two
trimming values).
Figure 10-25 shows the relationship between the trim bits and the resulting IRC1M frequency.