S12 Clock, Reset and Power Management Unit (S12CPMU)
7.3.2.20 S12CPMU IRC1M Trim Registers (CPMUIRCTRIMH / CPMUIRCTRIML)
0x02F8
15
14
13
12
11
10
9
8
R
W
0
0
TCTRIM[3:0]
IRCTRIM[9:8]
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 fIRC1M_TRIM
.
Figure 7-24. S12CPMU IRC1M Trim High Register (CPMUIRCTRIMH)
0x02F9
7
6
5
4
3
2
1
0
R
IRCTRIM[7:0]
W
Reset
F
F
F
F
F
F
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 fIRC1M_TRIM
.
Figure 7-25. S12CPMU IRC1M Trim Low Register (CPMUIRCTRIML)
Read: Anytime
Write: If PROT=0 (CPMUPROT register), then write anytime. Else write has no effect
NOTE
Writes to these registers while PLLSEL=1 clears the LOCK and UPOSC
status bits.
Table 7-20. CPMUIRCTRIMH/L Field Descriptions
Field
Description
15-12
IRC1M temperature coefficient Trim Bits
TCTRIM[3:0] Trim bits for the Temperature Coefficient (TC) of the IRC1M frequency.
Table 7-21 shows the influence of the bits TCTRIM3:0] on the relationship between frequency and temperature.
Figure 7-27 shows an approximate TC variation, relative to the nominal TC of the IRC1M (i.e. for
TCTRIM[3:0]=0000 or 1000).
9-0
IRC1M Frequency Trim Bits — Trim bits for Internal Reference Clock
IRCTRIM[9:0] After System Reset the factory programmed trim value is automatically loaded into these registers, resulting in a
Internal Reference Frequency fIRC1M_TRIM. See device electrical characteristics for value of fIRC1M_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 doe 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 7-26 shows the relationship between the trim bits and the resulting IRC1M frequency.
S12P-Family Reference Manual, Rev. 1.13
230
Freescale Semiconductor
FREESCALE [ Freescale ]
