Datasheet

Clock Generator Module (CGM)
MC68HC908AP Family Data Sheet, Rev. 4
92 Freescale Semiconductor
6.5.3 PLL Multiplier Select Registers
The PLL multiplier select registers (PMSH and PMSL) contain the programming information for the
modulo feedback divider.
MUL[11:0] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects the VCO frequency multiplier N.
(See 6.3.3 PLL Circuits and 6.3.6 Programming the PLL.) A value of $0000 in the multiplier select
registers configure the modulo feedback divider the same as a value of $0001. Reset initializes the
registers to $0040 for a default multiply value of 64.
NOTE
The multiplier select bits have built-in protection such that they cannot be
written when the PLL is on (PLLON = 1).
6.5.4 PLL VCO Range Select Register
The PLL VCO range select register (PMRS) contains the programming information required for the
hardware configuration of the VCO.
VRS[7:0] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear multiplier L which, in conjunction with
E(See6.3.3 PLL Circuits, 6.3.6 Programming the PLL, and 6.5.1 PLL Control Register.), controls the
hardware center-of-range frequency, f
VRS
. VRS[7:0] cannot be written when the PLLON bit in the
PCTL is set. (See 6.3.7 Special Programming Exceptions.) A value of $00 in the VCO range select
Address: $0038
Bit 7654321Bit 0
Read: 0 0 0 0
MUL11 MUL10 MUL9 MUL8
Write:
Reset:00000000
= Unimplemented
Figure 6-6. PLL Multiplier Select Register High (PMSH)
Address: $0039
Bit 7654321Bit 0
Read:
MUL7 MUL6 MUL5 MUL4 MUL3 MUL2 MUL1 MUL0
Write:
Reset:01000000
Figure 6-7. PLL Multiplier Select Register Low (PMSL)
Address: $003A
Bit 7654321Bit 0
Read:
VRS7 VRS6 VRS5 VRS4 VRS3 VRS2 VRS1 VRS0
Write:
Reset:01000000
Figure 6-8. PLL VCO Range Select Register (PMRS)