ELANSC300-33KI Datasheet

  • ELANSC300-33KI

  • Highly Integrated, Low-Power, 32-Bit Microcontroller

  • 1344.13KB

  • 139页

  • AMD

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P R E L I M I N A R Y
VOLTAGE PARTITIONING
The 脡lanSC300 microcontroller supports both 3.3-V
system designs and mixed 3.3-V and 5-V system de-
signs. For 3.3-V-only operation, all supply pins (VCC,
VCC1, VCC5, VMEM, VSYS, VSYS2, and AVCC)
should be connected to the 3.3-V DC supply. To oper-
ate an interface at 5 V, the VCCIO pins associated with
that I/O interface should be connected to 5 V. All supply
pins of the same name should be connected to the
same voltage plane. The different supply pins and their
functions are described in this section.
Refer to the Pin Characteristics section beginning on
page 24 of this data sheet for the internal VCC rail
(VCCIO and VCC Clamp) to which each pin is electri-
cally attached.
For more details about the information in this section,
see the commercial and industrial operating voltage
ranges beginning on page 80. Also see Table 51 on
page 99 and its corresponding notes.
鈥淭ypical Power Numbers鈥?on page 82 details the power
consumption of each of these supply pins in Maximum
ISA mode or Internal LCD mode.
operate at 3.3 V or 5 V, depending on the system de-
sign.
VSYS2
鈥?This supply pin controls the operating volt-
age for some of the LCD/alternate function pins. This
voltage pin should be connected to either 3.3 V or 5 V,
depending on the type of bus option selected, the volt-
age threshold requirements of attached devices, and
the state of the other voltage pins associated with the
LCD/alternate function interface pins (i.e., VCC1 and
VSYS).
AVCC
鈥?This supply pin provides power to the analog
section of the 脡lanSC300 microcontroller. It should al-
ways be connected to a low-noise 3.3-V supply. For
more information, see the DC characteristics specifica-
tions, beginning on page 80.
CRYSTAL SPECIFICATIONS
The 脡lanSC300 microcontroller on-chip oscillator is the
primary clock source driving all of the on-chip PLL
clock generators and the real-time clock (RTC) function
directly.
For problems with crystal startup, check that the spec-
ifications listed in this section are met, and refer to the
Troubleshooting Guide for Micro Power Off Mode on
脡lan
TM
SC300 and 脡lanSC310 Microcontrollers and
Evaluation Boards Application Note
, order #21810.
Externally, a parallel resonant PC/AT cut crystal
(32.768 kHz), two capacitors, and two resistors are re-
quired for the oscillator to function properly. It is critical
that the frequency of the oscillator circuit be as close as
possible to the nominal 32.768 kHz frequency for RTC
accuracy. By selecting the appropriate external circuit
components, this oscillator circuit can be made to op-
erate at very close to the nominal 32.768 kHz.
Figure 29 shows the complete oscillator circuit, includ-
ing the discrete component model for the crystal. In this
figure, the external discrete components that must be
supplied by the system designer are R
F
, R
B
, C
D
, C
G
,
and XTAL. R
F
is the external feedback resistor for the
on-chip amplifier. R
B
provides some isolation between
the parasitic capacitance of the chip and the crystal.
The value of this resistor also has a very small effect on
the operating frequency of the circuit. C
D
and C
G
are
the external load capacitors. The value of these capac-
itors, in conjunction with the other capacitive values
discussed below, have the most affect on the operating
frequency of this circuit.
The discrete components inside the dotted line repre-
sent the circuit model for the crystal, with C
O
represent-
ing the crystal lead shunt capacitance. The dashed line
component C
STRAY
represents the stray capacitance of
the printed circuit board. Typically, a crystal manufac-
turer provides values for all of the equivalent circuit
VCC
鈥?These supply pins are used to provide power
to the 脡lanSC300 microcontroller core only. They
should always be connected to a 3.3-V source.
VCC1
鈥?This supply pin provides power to a subset of
the LCD/alternate, power management, and ISA inter-
face pins. It can be connected to either a 3.3-V or 5-V
source, depending on the logic threshold requirements
of the external peripherals attached to these interfaces.
When connected to the 5-V supply, all outputs with
VCC1 as their VCCIO will be 5 V. If connected to 3.3 V,
all of these outputs will be 3.3 V.
VCC5
鈥?These supply pins are used to provide a 5-V
source for the 5-V input and output pins. If the system
design requires that the 脡lanSC300 microcontroller
support 5-V tolerant inputs, then this pin should be con-
nected to a 5-V DC source. This supply pin is the
VCCIO for the Parallel Port, Serial Port, and PCMCIA
interfaces.
VMEM
鈥?This supply pin controls the operating volt-
age of the memory interface. When connected to the
5-V supply, all outputs to the main memory will be 5 V.
This includes the 脡lanSC300 microcontroller data bus.
Therefore, translation buffers may be required when in-
terfacing to 5-V devices on the data bus when the
memory interface is operating at 3.3 V.
VSYS
鈥?These supply pins provide power to a subset
of the ISA address and command signal pins, external
memory chip selects, buffer direction controls, and
other miscellaneous functions. They can be required to
脡lan鈩C300 Microcontroller Data Sheet
95

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