Freescale Semiconductor, Inc.
Clock Functions
Bit 7
0
6
BCSP
0
5
BCSS
0
4
0
0
3
0
0
2
MCS
0
1
0
0
Bit 0
0
0
RESET:
0
CLKSEL — Clock Generator Clock select Register
$003D
Read and write anytime. Exceptions are listed below for each bit.
BCSP and BCSS bits determine the clock used by the main system
including the CPU and buses.
BCSP — Bus Clock Select PLL
0 = SYSCLK is derived from the crystal clock or from SLWCLK.
1 = SYSCLK source is the PLL.
Cannot be set when PLLON = 0. In limp-home mode, the output of
BCSP is forced to 1, but the BCSP bit reads the latched value.
BCSS — Bus Clock Select Slow
0 = SYSCLK is derived from the crystal clock EXTALi.
1 = SYSCLK source is the Slow clock SLWCLK.
This bit has no effect when BCSP is set.
MCS — Module Clock Select
0 = M clock is the same as PCLK.
1 = M clock is derived from Slow clock SLWCLK.
This bit determines the clock used by the ECT module and the baud
rate generators of the SCIs. In limp-home mode, the output of MCS is
forced to 0, but the MCS bit reads the latched value.
Advance Information
166
68HC(9)12D60 — Rev 4.0
Clock Functions
MOTOROLA
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MOTOROLA [ MOTOROLA ]
