MC68HC908EY16 Datasheet, PDF (99/278 Pages) Motorola, Inc – Microcontrollers

8.7.3 ICG Trim Register
Input/Output (I/O) Registers
Address: $0038
Bit 7
Read:
TRIM7
Write:
Reset:
1
6
5
4
3
2
TRIM6 TRIM5 TRIM4 TRIM3 TRIM2
0
0
0
0
0
Figure 8-13. ICG Trim Register (ICGTR)
1
TRIM1
0
Bit 0
TRIM0
0
TRIM7:TRIM0 — ICG Trim Factor Bits
These read/write bits change the size of the internal capacitor used by the internal clock generator. By
testing the frequency of the internal clock and incrementing or decrementing this factor accordingly,
the accuracy of the internal clock can be improved (see 20.9.1 Trimmed Internal Clock Generator
Characteristics). Incrementing this register by one decreases the frequency by 0.195 percent of the
unadjusted value. Decrementing this register by one increases the frequency by 0.195 percent. This
register cannot be written when the CMON bit is set. Reset sets these bits to $80, centering the range
of possible adjustment.
8.7.4 ICG Trim Value
Address: $FF80
Bit 7
6
5
4
3
2
1
Read:
TRIM7
Write:
TRIM6
TRIM5
TRIM4
TRIM3
TRIM2
TRIM1
Reset:
1
0
0
0
0
0
0
Figure 8-14. Internal Oscillator Trim Value (ICGT)
Bit 0
TRIM0
0
This register provides non-volatile storage for an optional oscillator trim value, which can be transferred
by the user software to the ICG Trim Register (ICGTR) when the device comes out of reset. (See 8.7.3
ICG Trim Register.)
8.7.5 ICG DCO Divider Register
Address: $0039
Bit 7
6
5
4
3
2
1
Read:
DDIV3 DDIV2 DDIV1
Write:
Reset:
0
0
0
0
U
U
U
= Unimplemented
U = Unaffected
Figure 8-15. ICG DCO Divider Control Register (ICGDVR)
Bit 0
DDIV0
U
DDIV3:DDIV0 — ICG DCO Divider Control Bits
These bits indicate the number of divide-by-twos (DDIV) that follow the digitally controlled oscillator.
When ICGON is set, DDIV is controlled by the digital loop filter. The range of valid values for DDIV is
from $0 to $9. Values of $A through $F are interpreted the same as $9. Since the DCO is active during
reset, reset has no effect on DSTG and the value may vary.
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
99