mm908e621 Freescale Semiconductor, Inc, mm908e621 Datasheet - Page 49

• Manufacturer Part Number: mm908e621
• Description: Integrated Quad Half-bridge And Triple High-side With Embedded Mcu And Lin For High End Mirror
• Manufacturer: Freescale Semiconductor, Inc

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” ($FF) state:
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
memory is explained
Internal Clock Generator (ICG) Trim Value
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 dependencies a ICG trim
values is located at address $FDC2. After trimming the ICG
is a range of typ. ±2% (±3% max.) at nominal conditions
(filtered (100nF) and stabilized (4,7uF) V
T
(V
Trim Register ICGTR at address $38 of the MCU.
Analog Integrated Circuit Device Data
Freescale Semiconductor
Ambient
DD
To enhance the ease-of-use of the 908E621, various
•$FD80:$FDDF Trim and Calibration Values
•$FFFE:$FFFF Reset Vector
In the event the application uses these parameters, one
Below the usage of the trim values located in the flash
The internal clock generator (ICG) module is used to
To trim the ICG this values has to be copied to the ICG
Important The value has to copied after every reset.
) as indicated in the 68HC908EY16 datasheet.
~25°C) and will vary over temperature and voltage
Table 14. Window Clear Interval
Window
$FDCF
Range
0
1
2
Select bits
WDP1:0
Period
00
01
10
11
00
01
10
11
00
01
10
11
min.
11.5
8.5
6.5
68
34
17
92
46
23
52
26
13
Watchdog Period
FACTORY TRIMMING AND CALIBRATION
max.
DD
11.5
15.5
t_wd
124
8.5
92
46
23
62
31
68
34
17
= 5V,
Unit
ms
ms
ms
t_open
11.5
5.75
15.5
7.75
4.25
8.5
Effective Open Window
46
23
62
31
34
17
Watchdog Period Range Value (AWD Trim)
code runaways.
the open window. Due to the high variation of the watchdog
period - and therefore the reduced width of the watchdog
window - a value is stored at address $FDCF. This value
classifies the watchdog period into 3 ranges (Range 0, 1, 2).
This allows the application software to select one out of three
time intervals to clear the watchdog based on the stored
value. The classification is done in a way that the application
software can have up to ±19% variation of the of optimal clear
interval, e.g. caused by ICG variation.
Effective Open Window
with a 50% open window results in effective open window,
which can be calculated by:
Optimal Clear Interval
the biggest possible variation to latest window open time and
to the earliest window closed time can be calculated with the
following formula:
watchdog based on the Window No. and chosen period.
The window watchdog supervises device recover from e.g.
The application software has to clear the watchdog within
Having a variation in the watchdog period in conjunction
latest window open time: t_open = t_wd max / 2
earliest window closed time: t_closed = t_wd min
The optimal clear interval - meaning the clear interval with
t_opt = t_open + (t_open+t_closed) / 2
See Table
t_closed
11.5
8.5
6.5
68
34
17
92
46
23
52
26
13
14
Unit
ms
ms
ms
to select the optimal clear interval for the
LOGIC COMMANDS AND REGISTERS
t_opt
14.25
7.125
19.25
9.625
10.75
5.375
28.5
38.5
21.5
FUNCTIONAL DEVICE OPERATION
57
77
43
Optimal Clear Interval
Unit
ms
ms
ms
variation
±19.3%
±19.5%
±20.9%
max.
908E621
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