mc68hc908rf2 Freescale Semiconductor, Inc, mc68hc908rf2 Datasheet - Page 90

• Manufacturer Part Number: mc68hc908rf2
• Description: M68hc08 Microcontrollers Microcontroller / Transmitter
• Manufacturer: Freescale Semiconductor, Inc

Internal Clock Generator Module (ICG)
6.7.2 ICG Multiplier Register
6.7.3 ICG Trim Register
Data Sheet
90
NOTE:
N6–N0 — ICG Multiplier Factor Bits
TRIM7–TRIM0 — ICG Trim Factor Bits
It is recommended that the user preserve a copy of the contents of the ICG trim
register (ICGTR) in non-volitale memory.
Address $7FEF is reserved for an optional factory-determined ICG trim value.
Consult with a local Motorola representative for more information and availability of
this option.
Address: $0037
Address: $0038
Reset:
Reset:
Read:
Read:
Write:
Write:
These read/write bits change the multiplier used by the internal
clock generator. The internal clock (ICLK) will be
(307.2 kHz ±25 percent) * N. A value of $00 in this register is interpreted the
same as a value of $01. This register cannot be written when the CMON bit is
set. Reset sets this factor to $15 (decimal 21) for default frequency of 6.45 MHz
±25 percent (1.613 MHz ±25 percent bus).
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 to ±2 percent. Incrementing this register by 1
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.
Freescale Semiconductor, Inc.
For More Information On This Product,
TRIM7
Bit 7
Bit 7
R
R
0
1
Internal Clock Generator Module (ICG)
Figure 6-12. ICG Multiplier Register (ICGMR)
= Reserved
Go to: www.freescale.com
TRIM6
Figure 6-13. ICG Trim Register (ICGTR)
N6
6
0
6
0
TRIM5
N5
5
0
5
0
TRIM4
N4
4
1
4
0
TRIM3
N3
3
0
3
0
TRIM2
N2
MC68HC908RF2 — Rev. 4.0
2
1
2
0
TRIM1
N1
1
0
1
0
MOTOROLA
TRIM0
Bit 0
Bit 0
N0
1
0