MPC555
/
MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-21
8.9.2.3 VDDSYN, VSSSYN
The charge pump and the VCO of the SPLL are fed by a separate 3.3-V power supply
(VDDSYN) in order to improve noise immunity and achieve a high stability in its output
frequency. VSSSYN provides an isolated ground reference for the PLL.
8.9.2.4 KAPWR
The oscillator, time base counter, decrementer, periodic interrupt timer and the real-
time clock are fed by the KAPWR rail. This allows the external power supply unit to
disconnect all other sub-units of the MCU in low-power deep-sleep mode. The TEXP
pin (fed by the same rail) can be used by the external power supply unit to switch be-
tween sources. The IRQ[6:7]/MODCK[2:3], IRQ[5]/MODCK1, XTAL, EXTAL, EXT-
CLK, PORESET, HRESET, SRESET, and RSTCONF/TEXP input pins are powered
by KAPWR. Circuits, including pull-up resisters, driving these inputs should be pow-
ered by KAPWR.
8.9.2.5 VDDA, VSSA
VDDA supplies power to the analog subsystems of the QADC_A and QADC_B mod-
ules; it is nominally 5.0 V. VDDA is the ground reference for the analog subsystems.
8.9.2.6 VPP
VPP supplies the programming and erase voltage for the CMF flash modules. It is
nominally 5.0 V for program or erase operations and can be lowered to a nominal 3.3
V for read operations.
8.9.2.7 VDDF, VSSF
VDDF provides internal power to the CMF flash module; it should be a nominal 3.3 V.
VSSF provides an isolated ground for the CMF flash module.
8.9.2.8 VDDH
VDDH provides power for the 5-V I/O operations. It is a nominal 5.0 V.
8.9.2.9 VDDSRAM
VDDSRAM supplies power to the 26-Kbyte SRAM module and the DPTRAM. It can
be used to keep the contents on the SRAM stable while the rest of the MPC555 /
MPC556 is powered down for standby operation.
8.9.2.10 VSS
VSS provides the ground reference for the MPC555 / MPC556.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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