ELANSC310 AMD [Advanced Micro Devices], ELANSC310 Datasheet - Page 84

• Manufacturer Part Number: ELANSC310
• Description: Single-Chip, 32-Bit, PC/AT Microcontroller
• Manufacturer: AMD [Advanced Micro Devices]

VOLTAGE PARTITIONING
The ÉlanSC310 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 21 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 70. Also see Table 45 on
page 88 and its corresponding notes.
“Typical Power Numbers” on page 72 details the power
consumption of each of these supply pins in Maximum
ISA mode.
VCC — These supply pins are used to provide power
to the ÉlanSC310 microcontroller core only. They
should always be connected to a 3.3-V source.
VCC1 — This supply pin provides power to a subset of
the power management and ISA interface pins. It can
be connected to either a 3.3-V or 5-V source, depend-
ing on the logic threshold requirements of the external
peripherals attached to these interfaces. When con-
nected 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 — 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 ÉlanSC310 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 and Serial Port interfaces.
VMEM — 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 ÉlanSC310 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 — 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
operate at 3.3 V or 5 V, depending on the system de-
sign.
84
Élan™SC310 Microcontroller Data Sheet
P R E L I M I N A R Y
VSYS2 — This voltage pin should be connected to ei-
ther 3.3 V or 5 V, depending on the type of bus option
selected, the voltage threshold requirements of at-
tached devices, and the state of the other voltage pins
associated with the alternate function interface pins
(i.e., VCC1 and VSYS).
AVCC — This supply pin provides power to the analog
section of the ÉlanSC310 microcontroller. It should al-
ways be connected to a low-noise 3.3-V supply.
For more information, see the DC characteristics be-
ginning on page 70.
CRYSTAL SPECIFICATIONS
The ÉlanSC310 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
Élan
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
and XTAL. R
on-chip amplifier. R
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
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
ing the crystal lead shunt capacitance. The dashed line
component C
the printed circuit board. Typically, a crystal manufac-
turer provides values for all of the equivalent circuit
model components for a given crystal (i.e., L
and C
turer will provide a load capacitance specification usu-
al l y de s ig n at ed as C
specification is the capacitive load at which the manu-
facturer has tuned the crystal for the specified
TM
O
SC300 and ÉlanSC310 Microcontrollers and
). In addition to these parameters, the manufac-
F
STRAY
is the external feedback resistor for the
represents the stray capacitance of
B
provides some isolation between
L
. Th e lo ad c ap a ci t an c e
F
, R
D
O
and C
represent-
B
, C
1
, C
D
G
1
, C
, R
are
G
1
,
,