cs5535 National Semiconductor Corporation, cs5535 Datasheet - Page 51

• Manufacturer Part Number: cs5535
• Description: Geode Cs5535 Companion Multi-function South Bridge
• Manufacturer: National Semiconductor Corporation

Revision 0.8
Global Concepts and Features
When a request packet arrives from a Request Out (RO)
port, the address and other attributes in the packet are
used to look up the destination port. If the port Request In
(RI) is available, the request is passed. If there are multiple
requests, priorities are used to establish which requestor
and destination port utilize the transfer cycle. A transfer
from an RO to an RI takes one clock edge.
3.1.3
Earlier in this section, it was indicated that an RO can be
used to present a write data packet or a read response
packet. The use and need of a read response packet for a
read request is obvious. However, there is also an optional
write response packet. This tells the requestor that the
write has completed. This is used to hold a processor I/O
write instruction until the response is received, that is, I/O
writes are never posted. Memory writes are always posted.
The response packet is also used to generate Synchro-
nous System Management Interrupts (SSMIs). System
Management Mode (SMM) is used for hardware emulation
and other traps. An SSMI can be generated by a GLD or
via special GLIU descriptors. When the response arrives
back at the processor, interface circuits generate an SMI to
invoke the SMM software. Lastly, all response packets con-
tain an exception flag that can be set to indicate an error.
GLPCI_SB
Response Packets
USBC1
USBC2
GLCP
ATAC
ACC
DD
& Error
& Error
& Error
& Error
& Error
& Error
& Error
& Error
ASMI
ASMI
ASMI
ASMI
ASMI
ASMI
ASMI
ASMI
Figure 3-2. GeodeLink Architecture ASMI and Error Routing
GLIU ASMI & Error
(Continued)
51
3.1.4
Two additional signals are needed to complete this
GeodeLink architecture overview: Asynchronous System
Management Interrupt (ASMI) and Error. Each GLD out-
puts these ASMI and Error signals.
An ASMI is much like a legacy interrupt, except it invokes
the SMM handler. As the name suggests, an ASMI is an
asynchronous event, while an SSMI is synchronous to the
instruction that generated it.
The Error signal simply indicates some type of unexpected
error has occurred. A device asserts this signal when an
unexpected error occurs. In a normal operating system,
this would not be asserted. For example, a disk read error
or ethernet network error would be signaled using normal
GeodeLink packet mechanisms. This signal is reserved for
the truly unexpected.
Each GLD has mechanisms for enabling and mapping mul-
tiple internal sources down to these singular outputs. The
mechanism consists of the logical “OR” of all enabled
sources. The GLIU receives the ASMI and Error pair from
each GLD. It has the same “OR” and enable mechanism
that finally results in a single ASMI and Error pair for the
whole component (see Figure 3-2). The ASMI is routed to
the processor, while the Error is routed to the GLCP. Within
the GLCP, the Error signal can be mapped into an ASMI for
routing back into the GLIU.
ASMI and Error
CS5535 Error to GLCP Debug
CS5535 ASMI to GX2
or conversion to ASM
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