mc9s08gt32a Freescale Semiconductor, Inc, mc9s08gt32a Datasheet - Page 121

• Manufacturer Part Number: mc9s08gt32a
• Description: Hcs08 Microcontrollers 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

In this particular case, the MCU has been attached to a PCB and the entire assembly is undergoing final
test with automated test equipment. A separate signal or message is provided to the MCU operating under
user provided software control. The MCU initiates a trim procedure as outlined in
tester supplies a precision reference signal.
If the intended bus frequency is near the maximum allowed for the device, it is recommended to trim using
a reduction divisor (R) twice the final value. Once the trim procedure is complete, the reduction divisor
can be restored. This will prevent accidental overshoot of the maximum clock frequency.
7.5
Refer to the direct-page register summary in
address assignments for all ICG registers. This section refers to registers and control bits only by their
names. A Freescale-provided equate or header file is used to translate these names into the appropriate
absolute addresses.
Freescale Semiconductor
Initial conditions:
1) Clock supplied from ATE has 500 μs duty period
2) ICG configured for internal reference with 4 MHz bus
ICG Registers and Control Bits
INCREASES THE FREQUENCY)
(DECREASING ICGTRM
ICGTRM - 128 / (2**n)
COUNT < EXPECTED = 500
(RUNNING TOO SLOW)
ICGTRM =
MC9S08GB60A Data Sheet, Rev. 1.02
n = n + 1
IS n > 8?
Figure 7-11. Trim Procedure
(COUNT = # OF BUS CLOCKS / 4)
DECREASES THE FREQUENCY)
NO
START TRIM PROCEDURE
INCOMING CLOCK WIDTH
(INCREASING ICGTRM
ICGTRM = $80, n = 1
ICGTRM + 128 / (2**n)
CASE STATEMENT
Chapter 4,
ICGTRM =
MEASURE
YES
.
COUNT > SZZEXPECTED = 500
(RUNNING TOO FAST)
“Memory” of this data sheet for the absolute
COUNT = EXPECTED = 500
ICG Registers and Control Bits
Figure 7-11
STORE ICGTRM VALUE
IN NON-VOLATILE
CONTINUE
MEMORY
while the
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