Table of Contents
Advertisement
• When using a 32.768 kHz external reference, if the maximum mid-range DCO
frequency that can be achieved with a 32.768 kHz reference is desired, set
C4[DRST_DRS] bits to 2'b01 and set C4[DMX32] bit to 1. The resulting DCO
output (MCGOUTCLK) frequency with the new multiplier of 1464 will be 48
MHz.
• When using a 32.768 kHz external reference, if the maximum mid high-range
DCO frequency that can be achieved with a 32.768 kHz reference is desired, set
C4[DRST_DRS] bits to 2'b10 and set C4[DMX32] bit to 1. The resulting DCO
output (MCGOUTCLK) frequency with the new multiplier of 2197 will be 72
MHz.
• When using a 32.768 kHz external reference, if the maximum high-range DCO
frequency that can be achieved with a 32.768 kHz reference is desired, set
C4[DRST_DRS] bits to 2'b11 and set C4[DMX32] bit to 1. The resulting DCO
output (MCGOUTCLK) frequency with the new multiplier of 2929 will be 96
MHz.
5. Wait for the FLL lock time to guarantee FLL is running at new C4[DRST_DRS] and
C4[DMX32] programmed frequency.
To change from FEI clock mode to FBI clock mode, follow this procedure:
1. Change C1[CLKS] bits in C1 register to 2'b01 so that the internal reference clock is
selected as the system clock source.
2. Wait for S[CLKST] bits in the MCG status register to change to 2'b01, indicating
that the internal reference clock has been appropriately selected.
3. Write to the C2 register to determine the IRCS output (IRCSCLK) frequency range.
• By default, with C2[IRCS] cleared to 0, the IRCS selected output clock is the
slow internal reference clock (32 kHz IRC). If the faster IRC is desired, set
C2[IRCS] to 1 for a IRCS clock derived from the 4 MHz IRC source.
30.5.2 Using a 32.768 kHz reference
In FEE and FBE modes, if using a 32.768 kHz external reference, at the default FLL
multiplication factor of 640, the DCO output (MCGFLLCLK) frequency is 20.97 MHz at
low-range.
Freescale Semiconductor, Inc.
KV4x Reference Manual, Rev. 2, 02/2015
Preliminary
Chapter 30 Multipurpose Clock Generator (MCG)
571
Advertisement
Table of Contents
