MC68HC08AS32A Datasheet, PDF (110/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Clock Generator Module (CGM)
Address: $001E
Bit 7
Read:
MUL7
Write:
Reset: 0
6
MUL6
1
5
MUL5
1
4
MUL4
0
3
VRS7
0
2
VRS6
1
1
VRS5
1
Figure 5-6. PLL Programming Register (PPG)
Bit 0
VRS4
0
MUL[7:4] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects the VCO
frequency multiplier, N. (See 5.3.2 Phase-Locked Loop Circuit (PLL).) A value
of $0 in the multiplier select bits configures the modulo feedback divider the
same as a value of $1. Reset initializes these bits to $6 to give a default multiply
value of 6.
Table 5-1. VCO Frequency Multiplier (N) Selection
MUL7:MUL6:MUL5:MUL4
0000
0001
0010
0011
VCO Frequency Multiplier (N)
1
1
2
3
NOTE:
NOTE:
1101
13
1110
14
1111
15
The multiplier select bits have built-in protection that prevents them from being
written when the PLL is on (PLLON = 1).
VRS[7:4] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear multiplier, L,
which controls the hardware center-of-range frequency, f_VRS, (see 5.3.2
Phase-Locked Loop Circuit (PLL)). VRS[7:4] cannot be written when the
PLLON bit in the PLL control register (PCTL) is set. (See 5.3.2.5 Special
Programming Exceptions.) A value of $0 in the VCO range selects bits,
disables the PLL, and clears the BCS bit in the PCTL. (See 5.3.3 Base Clock
Selector Circuit and 5.3.2.5 Special Programming Exceptions for more
information.) Reset initializes the bits to $6 to give a default range multiply value
of 6.
The VCO range select bits have built-in protection that prevents them from being
written when the PLL is on (PLLON = 1) and prevents selection of the VCO clock
as the source of the base clock (BCS = 1) if the VCO range select bits are all clear.
The VCO range select bits must be programmed correctly. Incorrect programming
can result in failure of the PLL to achieve lock.
Data Sheet
110
Clock Generator Module (CGM)
For More Information On This Product,
Go to: www.freescale.com
MC68HC08AS32A — Rev. 1
MOTOROLA