MPC555
/
MPC556
SIGNAL DESCRIPTIONS
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
2-28
2.3.8.3 VDDI
Pin Name
: vddi
VDDI –
3-V voltage supply input for internal logic.
2.3.8.4 VSSI
Pin Name
: vssi
VSSI –
Zero supply input for internal logic. In packaged devices, VSSI is not a sepa-
rate input from VSS.
2.3.8.5 KAPWR
Pin Name
: kapwr
Keep-Alive Power –
3-V voltage supply input for the oscillator and keep-alive regis-
ters.
2.3.8.6 VDDSRAM
Pin Name
: vddsram
SRAM Keep-Alive Power –
3-V voltage supply input for the SRAM.
2.3.8.7 VSS
Pin Name
: vss
VSS –
Ground level reference input.
2.4 Reset State
All input pins, with the exception of the power supply and clock related pins, are “weak-
ly pulled” to a value during reset by a 130-microampere resistor based on certain con-
ditions. In reset state all I/O pins become inputs, and all outputs except clkout,
hreset_b, sreset_b, will be pulled only by the pull-up/pull-down.
2.4.1 Pin Functionality Out of Reset
The functionality out of reset of some pins that support multiple functionality is defined
in the SIUMCR through the reset configuration word. For details on which multiplexed
pins are configured by the reset configuration word and how they are configured, refer
to
7.5.2 Hard Reset Configuration Word
The 3-V related pins have selectable output buffer drive strengths which are controlled
by the COM[0] bit in the USIU’s system clock and reset control register (SCCR). The
control is as follows:
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..