mc9s12q128 Freescale Semiconductor, Inc, mc9s12q128 Datasheet - Page 549

• Manufacturer Part Number: mc9s12q128
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

then FCLKDIV register bits PRDIV8 and FDIV[5:0] are to be set as described in
For example, if the oscillator clock frequency is 950 kHz and the bus clock is 10 MHz, FCLKDIV bits
FDIV[5:0] should be set to 4 (000100) and bit PRDIV8 set to 0. The resulting FCLK is then 190 kHz. As
a result, the Flash algorithm timings are increased over optimum target by:
Command execution time will increase proportionally with the period of FCLK.
If the FCLKDIV register is written, the bit FDIVLD is set automatically. If the FDIVLD bit is 0, the
FCLKDIV register has not been written since the last reset. If the FCLKDIV register has not been written
to, the Flash command loaded during a command write sequence will not execute and the ACCERR flag
in the FSTAT register will set.
Freescale Semiconductor
200 190
–
Because of the impact of clock synchronization on the accuracy of the
functional timings, programming or erasing the Flash array cannot be
performed if the bus clock runs at less than 1 MHz. Programming or erasing
the Flash array with an input clock < 150 kHz should be avoided. Setting
FCLKDIV to a value such that FCLK < 150 kHz can destroy the Flash array
due to overstress. Setting FCLKDIV to a value such that (1/FCLK + Tbus)
< 5 s can result in incomplete programming or erasure of the Flash array
cells.
200 100
=
5%
MC9S12Q128
CAUTION
Rev 1.09
Chapter 19 96 Kbyte Flash Module (S12FTS96KV1)
Figure
19-21.
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