MC9S12HZ256 Datasheet, PDF (79/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

START
Chapter 2 256 Kbyte Flash Module (FTS256K2V1)
Tbus < 1µs?
NO
ALL COMMANDS IMPOSSIBLE
YES
PRDIV8=0 (reset)
OSCILLATOR
CLOCK
NO
> 12.8 MHZ?
YES
PRDIV8=1
PRDCLK=oscillator_clock/8
PRDCLK=oscillator_clock
PRDCLK[MHz]*(5+Tbus[µs]) ^NO
an integer?
YES
FDIV[5:0]=INT(PRDCLK[MHz]*(5+Tbus[µs]))
FDIV[5:0]=PRDCLK[MHz]*(5+Tbus[µs])-1
TRY TO DECREASE Tbus FCLK=(PRDCLK)/(1+FDIV[5:0])
1/FCLK[MHz] + Tbus[µs] > 5
AND
FCLK > 0.15 MHz
?
YES
END
NO
YES
FDIV[5:0] > 4?
NO
ALL COMMANDS IMPOSSIBLE
Figure 2-22. Determination Procedure for PRDIV8 and FDIV Bits
MC9S12HZ256 Data Sheet, Rev. 2.04
Freescale Semiconductor
79