908E626 Datasheet, PDF (29/38 Pages) Freescale Semiconductor, Inc – Integrated Stepper Motor Driver with Embedded MCU and LIN Serial Communication

FUNCTIONAL DEVICE OPERATION
FACTORY TRIMMING AND CALIBRATION
To enhance the ease-of-use of the 908E626, various
parameters (e.g. ICG trim value) are stored in the flash
memory of the device. The following flash memory locations
are reserved for this purpose and might have a value different
from the empty (0xFF) state:
• 0xFD80:0xFDDF Trim and Calibration Values
• 0xFFFE:0xFFFF Reset Vector
In the event the application uses these parameters, one
has to take care not to erase or override these values. If these
parameters are not used, these flash locations can be erased
and otherwise used.
Trim Values
Below the usage of the trim values located in the flash
memory is explained
Internal Clock Generator (ICG) Trim Value
The internal clock generator (ICG) module is used to
create a stable clock source for the microcontroller without
using any external components. The untrimmed frequency of
the low-frequency base clock (IBASE), will vary as much as
±25 percent due to process, temperature, and voltage
dependencies. To compensate this dependancies a ICG trim
values is located at adress $FDC2. After trimming the ICG is
a range of typ. ±2% (±3% max.) at nominal conditions (filtered
(100nF) and stabilized (4,7uF) V_DD = 5V, T_Ambient~25°C) and
will vary over temperature and voltage (VDD) as indicated in
the 68HC908EY16 datasheet.
To trim the ICG this values has to be copied to the ICG
Trim Register ICGTR at adress $38 of the MCU.
Important The value has to be copied after every reset.
Analog Integrated Circuit Device Data
Freescale Semiconductor
908E626
29