MC908GR32AVFAE Datasheet, PDF (80/314 Pages) Freescale Semiconductor, Inc – Microcontrollers

Clock Generator Module (CGM)
4.4.9 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks.
CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by two or the VCO clock, CGMVCLK,
divided by two.
4.4.10 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
4.5 CGM Registers
These registers control and monitor operation of the CGM:
• PLL control register (PCTL) — see 4.5.1 PLL Control Register
• PLL bandwidth control register (PBWC) — see 4.5.2 PLL Bandwidth Control Register
• PLL multiplier select register high (PMSH) — see 4.5.3 PLL Multiplier Select Register High
• PLL multiplier select register low (PMSL) — see 4.5.4 PLL Multiplier Select Register Low
• PLL VCO range select register (PMRS) — see 4.5.5 PLL VCO Range Select Register
Figure 4-3 is a summary of the CGM registers.
Addr.
Register Name
Bit 7
6
5
$0036
PLL Control Register ^Read:
(PCTL) Write:
See page 81. _Reset:
PLLIE
0
PLLF
PLLON
0
1
PLL Bandwidth Control ^Read: _AUTO
LOCK
ACQ
$0037
Register (PBWC) Write:
See page 82. _{Reset: 0}
0
0
PLL Multiplier Select High ^{Read: 0}
0
0
$0038
Register (PMSH) Write:
See page 83. _{Reset: 0}
0
0
$0039
PLL Multiplier Select Low ^Read:
Register (PMSL) Write:
See page 84. _Reset:
MUL7
0
MUL6
1
MUL5
0
$003A
PLL VCO Select Range ^Read:
Register (PMRS) Write:
See page 84. _Reset:
VRS7
0
VRS6
1
VRS5
0
Read: 0
0
0
$003B
Reserved Register Write:
Reset: 0
0
0
= Unimplemented
NOTES:
1. When AUTO = 0, PLLIE is forced clear and is read-only.
2. When AUTO = 0, PLLF and LOCK read as clear.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS7:VRS0 = $0, BCS is forced clear and is read-only.
5. When PLLON = 1, the PLL programming register is read-only.
6. When BCS = 1, PLLON is forced set and is read-only.
4
3
BCS
R
0
0
0
0
0
0
0
MUL11
0
0
MUL4
MUL3
0
0
VRS4
VRS3
0
0
0
R
0
0
R = Reserved
Figure 4-3. CGM I/O Register Summary
2
R
0
0
0
MUL10
0
MUL2
0
VRS2
0
R
0
1
VPR1
0
0
0
MUL9
0
MUL1
0
VRS1
0
R
0
Bit 0
VPR0
0
R
0
MUL8
0
MUL0
0
VRS0
0
R
1
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
80
Freescale Semiconductor