MC68HC908AS60ACFN FREESCALE [Freescale Semiconductor, Inc], MC68HC908AS60ACFN Datasheet - Page 138

• Manufacturer Part Number: MC68HC908AS60ACFN
• Description: M68HC08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Clock Generator Module (CGM)
XLD — Crystal Loss Detect Bit
Bits 3–0 — Reserved for Test
10.5.3 PLL Programming Register
The PLL programming register contains the programming information for the modulo feedback divider
and the programming information for the hardware configuration of the VCO.
MUL7–MUL4 — Multiplier Select Bits
138
In automatic bandwidth control mode (AUTO = 1), the last-written value from manual operation is
stored in a temporary location and is recovered when manual operation resumes. Reset clears this bit,
enabling acquisition mode.
When the VCO output, CGMVCLK, is driving CGMOUT, this read/write bit can indicate whether the
crystal reference frequency is active or not.
To check the status of the crystal reference, do the following:
The crystal loss detect function works only when the BCS bit is set, selecting CGMVCLK to drive
CGMOUT. When BCS is clear, XLD always reads as logic 0.
These bits enable test functions not available in user mode. To ensure software portability from
development systems to user applications, software should write 0s to bits 3–0 when writing to PBWC.
These read/write bits control the modulo feedback divider that selects the VCO frequency multiplier,
N. (See
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.
1 = Tracking mode
0 = Acquisition mode
1 = Crystal reference not active
0 = Crystal reference active
1. Write a 1 to XLD.
2. Wait N × 4 cycles. N is the VCO frequency multiplier.
3. Read XLD.
10.3.2.1 Circuits
Address:
Reset:
Read:
Write:
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
$001E
MUL7
Bit 7
0
Figure 10-6. PLL Programming Register (PPG)
and
MUL6
10.3.2.4 Programming the
6
1
MUL5
5
1
MUL4
4
0
PLL). A value of $0 in the multiplier select bits
VRS7
3
0
VRS6
2
1
VRS5
1
1
Freescale Semiconductor
VRS4
Bit 0
0