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Architecture Overview
(Continued)
LPC: See Section 2.4.8 "Low Pin Count (LPC) Bus Inter-
face Signals" on page 67.
Sub-ISA: See Section 2.4.7 "Sub-ISA Interface Signals"
on page 66, Section 5.2.5 "Sub-ISA Bus Interface" on
page 156, and Section 3.2 "Multiplexing, Interrupt Selec-
tion, and Base Address Registers" on page 81
GPIO: See Section 2.4.16 "GPIO Interface Signals" on
page 75.
More detailed information about each of these interfaces
is provided in Section 5.2 "Module Architecture" on page
151.
Super/IO Block Interfaces: See Section 3.2 "Multi-
plexing, Interrupt Selection, and Base Address Regis-
ters" on page 81, Section 2.4.5 "ACCESS.bus Interface
Signals" on page 60, Section 2.4.13 "Fast Infrared (IR)
Port Interface Signals" on page 72, and Section 2.4.12
"Parallel Port Interface Signals" on page 71.
The Core Logic module interface to the GX1 module con-
sists of seven miscellaneous connections, the PCI bus
interface signals, plus the display controller connections.
Note that the PC/AT legacy signals NMI, WM_RST, and
A20M are all virtual functions executed in SMM (System
Management Mode) by the BIOS.
PSERIAL is a one-way serial bus from the GX1 to the
Core Logic module used to communicate power-
management states and VSYNC information for VGA
emulation.
IRQ13 is an input from the processor indicating that a
floating point error was detected and that INTR should
be asserted.
INTR is the level output from the integrated 8259A PICs
and is asserted if an unmasked interrupt request (IRQn)
is sampled active.
SMI# is a level-sensitive interrupt to the GX1 that can be
configured to assert on a number of different system
events. After an SMI# assertion, SMM is entered and
program execution begins at the base of the SMM
address space. Once asserted, SMI# remains active
until the SMI source is cleared.
SUSP# and SUSPA# are handshake signals for imple-
menting CPU Clock Stop and clock throttling.
CPU_RST resets the CPU and is asserted for approxi-
mately 100 μs after the negation of POR#.
PCI bus interface signals.
1.4
The SuperI/O (SIO) module is a member of National Semi-
conductor’s SuperI/O family of integrated PC peripherals. It
is a PC98 and ACPI compliant SIO that offers a single-cell
solution to the most commonly used ISA peripherals.
SUPERI/O MODULE
The SIO module incorporates: two Serial Ports, an Infrared
Communication Port that supports FIR, MIR, HP-SIR,
Sharp-IR, and Consumer Electronics-IR, a full IEEE 1284
Parallel Port, two ACCESS.bus
Interface (ACB) ports, Sys-
tem Wakeup Control (SWC), and a Real-Time Clock (RTC)
that provides RTC timekeeping.
1.5
In addition to the four main modules (i.e., GX1, Core Logic,
Video Processor and SIO) that make up the SC2200, the
following blocks of logic have also been integrated into the
SC2200:
CLOCK, TIMERS, AND RESET LOGIC
Clock Generators as described in Section 3.5 "Clock
Generators and PLLs" on page 93.
Configuration Registers as described in Section 3.2
"Multiplexing, Interrupt Selection, and Base Address
Registers" on page 81.
A WATCHDOG timer as described in Section 3.3
"WATCHDOG" on page 88.
A High-Resolution timer as described in Section 3.4
"High-Resolution Timer" on page 91.
1.5.1
This section provides a description of the reset flow of the
SC2200.
Reset Logic
1.5.1.1
Power-On reset is triggered by assertion of the POR# sig-
nal. Upon power-on reset, the following things happen:
Power-On Reset
Strap balls are sampled.
PLL4, PLL5, and PLL6 are reset, disabling their output.
When the POR# signal is negated, the clocks lock and
then each PLL outputs its clock. PLL6 is the last clock
generator to output a clock. See Section 3.5 "Clock
Generators and PLLs" on page 93.
Certain WATCHDOG and High-Resolution Timer
register bits are cleared.
1.5.1.2
System reset causes signal PCIRST# to be issued, thus
triggering reset of all PCI and LPC agents. A system reset
is triggered by any of the following events:
System Reset
Power-on, as indicated by POR# signal assertion.
A WATCHDOG reset event (see Section 3.3.2
"WATCHDOG Registers" on page 89).
Software initiated system reset.