mcf54455 Freescale Semiconductor, Inc, mcf54455 Datasheet - Page 20

• Manufacturer Part Number: mcf54455
• Description: 32-bit Microprocessor With Usb On-the-go, Ethernet, Pci, Ddr2/ddr Controller And Encryption
• Manufacturer: Freescale Semiconductor, Inc

Electrical Characteristics
5.5
The clock module configures the device for one of several clocking methods. Clocking modes include internal phase-locked
loop (PLL) clocking with an external clock reference or an external crystal reference supported by an internal crystal amplifier.
The PLL can also be disabled, and an external oscillator can directly clock the device.
The specifications in
specification is based on an acceptable tolerance for the PLL, which yields 50% duty-cycle internal clocks to all on-chip
peripherals. The MCF5445x devices use the input clock signal as its synchronous bus clock for PCI. A poor duty cycle on the
input clock, may affect the overall timing margin to external devices. If negative edge logic is used to interface to PCI, providing
a 50% duty-cycle input clock aids in simplifying overall system design.
20
1
2
3
4
5
6
Weak Internal Pull Up Device Current, tested at V
Input Capacitance
Load Capacitance
DC Injection Current
IV
specification for an example circuit. There are three PV
PV
Refer to the MCF54455 Reference Manual signals description chapter for pins having weak internal pull-up devices.
This parameter is characterized before qualification rather than 100% tested.
All functional non-supply pins are internally clamped to V
Input must be current limited to the value specified. To determine the value of the required current-limiting resistor,
calculate resistance values for positive and negative clamp voltages, then use the larger of the two values.
Power supply must maintain regulation within operating V
current conditions. If positive injection current (V
and could result in external power supply going out of regulation. Ensure the external V
than the maximum injection current. This is the greatest risk when the MCU is not consuming power. Examples are: if
no system clock is present, or if clock rate is very low which would reduce overall power consumption. Also, at power-up,
the system clock is not present during the power-up sequence until the PLL has attained lock.
All input-only pins
All input/output (three-state) pins
High drive strength
Single Pin Limit
Total MCU Limit, Includes sum of all stressed pins
Low drive strength
DD
DD
V
and PV
NEGCLAMP
ClockTiming Specifications
input.
1 / C1 Frequency
Item
C1
C2
C3
C4
DD
Table 9
should be at the same voltage. PV
=V
3
Cycle time
Rise time (20% of vdd to 80% of vdd)
Fall time (80% of vdd to 20% of vdd)
Duty cycle (at 50% of vdd)
SS
3, 4, 5, 6
– 0.3 V, V
are for the CLKIN input pin (EXTAL input driven by an external clock reference). The duty cycle
Characteristic
MCF5445x ColdFire
POSCLAMP
Table 9. Input Clock Timing Requirements
Specification
Table 8. DC Electrical Specifications
= V
DD
IL
in
®
+ 0.3
Max.
> V
DD
Microprocessor Data Sheet, Rev. 0
should have a filtered input. Please see the PLL section of this
DD
2
DD
) is greater than I
SS
DD
inputs, one for each PLL. A filter circuit should used on each
and their respective V
range during instantaneous and operating maximum
Symbol
I
APU
C
C
I
Min
DD
IC
15
25
40
in
L
-
-
, the injection current may flow out of V
DD
.
66.66
Max
Min
-1.0
40
60
–10
DD
-10
2
2
—
—
load shunts current greater
Freescale Semiconductor
MHz
Unit
ns
ns
ns
%
–130
Max
1.0
25
50
10
7
7
Units
mA
μA
pF
pF
DD