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Architecture Overview
• USB: See Section 6.2.4 "Universal Serial Bus" on page
147. The USB function uses signal AD29 as the IDSEL
for PCI configuration.
• LPC: See Section 3.4.9 "Low Pin Count (LPC) Bus Inter-
face Signals" on page 60.
• Sub-ISA: See Section 3.4.8 "Sub-ISA Interface Signals"
on page 59, Section 6.2.5 "Sub-ISA Bus Interface" on
page 147, and Section 4.2 "Pin Multiplexing, Interrupt
Selection, and Base Address Registers" on page 72
• GPIO: See Section 3.4.17 "GPIO Interface Signals" on
page 67.
More detailed information about each of these interfaces is
provided in Section 6.2 "Module Architecture" on page 142.
• Super/IO Block Interfaces: See Section 4.2 "Pin Multi-
plexing, Interrupt Selection, and Base Address Regis-
ters" on page 72, Section 3.4.6 "ACCESS.bus Interface
Signals" on page 55, Section 3.4.14 "Fast Infrared (IR)
Port Interface Signals" on page 64, and Section 3.4.13
"Parallel Port Interface Signals" on page 63.
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.
AMD Geode™ SC1200/SC1201 Processor Data Book
2.4
SuperI/O Module
The SuperI/O (SIO) module is a PC98 and ACPI compliant
SIO that offers a single-cell solution to the most commonly
used ISA peripherals.
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.
2.5
Clock, Timers, and Reset Logic
In addition to the four main modules (i.e., GX1, Core Logic,
Video Processor and SIO) that make up the SC1200/
SC1201 processor, the following blocks of logic have also
been integrated:
• Clock Generators as described in Section 4.5 "Clock
Generators and PLLs" on page 83.
• Configuration Registers as described in Section 4.2 "Pin
Multiplexing, Interrupt Selection, and Base Address
Registers" on page 72.
• A WATCHDOG timer as described in Section 4.3
"WATCHDOG" on page 79.
• A High-Resolution timer as described in Section 4.4
"High-Resolution Timer" on page 81.
2.5.1
Reset Logic
This section provides a description of the reset flow of the
SC1200/SC1201 processor.
2.5.1.1
Power-On Reset
Power-on reset (POR) is triggered by assertion of the
POR# signal. Upon power-on reset, the following things
happen:
• 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 4.5 "Clock
Generators and PLLs" on page 83.
• Certain WATCHDOG and High-Resolution Timer
register bits are cleared.
2.5.1.2
System Reset
System reset causes signal PCIRST# to be issued, thus
triggering a reset of all PCI and LPC agents. A system
reset is triggered by any of the following events:
• Power-on, as indicated by POR# signal assertion.
• A WATCHDOG reset event (see Section 4.3.2
"WATCHDOG Registers" on page 80).
• Software initiated system reset.
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