XC908AS60ACFU Motorola Semiconductor Products, XC908AS60ACFU Datasheet - Page 195

• Manufacturer Part Number: XC908AS60ACFU
• Description: MC68HC908AZ60A, MC68HC908AS60A Hcmos Microcontroller Unit Technical Data
• Manufacturer: Motorola Semiconductor Products

MC68HC908AZ60A — Rev 2.0
MOTOROLA
NOTE:
In manual mode, it is usually necessary to wait considerably longer than
t
on page 179), because the factors described in
on Reaction Time
When defining a limit in software for the maximum lock time, the value
must allow for variation due to all of the factors mentioned in this section,
especially due to the C
The calculated lock time is only an indication and it is the customer’s
responsibility to allow enough of a guard band for their application. Prior
to finalizing any software and while determining the maximum lock time,
take into account all device to device differences. Typically, applications
set the maximum lock time as an order of magnitude higher than the
measured value. This is considered sufficient for all such device to
device variation.
Motorola recommends measuring the lock time of the application system
by utilizing dedicated software, running in FLASH, EEPROM or RAM.
This should toggle a port pin when the PLL is first configured and
switched on, then again when it goes from acquisition to lock mode and
finally again when the PLL lock bit is set. The resultant waveform can be
captured on an oscilloscope and used to determine the typical lock time
for the microcontroller and the associated external application circuit.
e.g.
The filter capacitor should be fully discharged prior to making any
measurements.
Lock
Init. low
before selecting the PLL clock (see
Clock Generator Module (CGM)
t
ACQ
on page 192, may slow the lock time considerably.
t
F
LOCK
capacitor and application specific influences.
t
AL
Acquisition/Lock Time Specifications
Base Clock Selector Circuit
t
PLL Configured and switched on
t
TRK
ACQ
Signal on port pin
Clock Generator Module (CGM)
Complete and Lock Set
Complete
Parametric Influences
Technical Data
195