cs5535 National Semiconductor Corporation, cs5535 Datasheet - Page 68

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

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Global Concepts and Features
3.8.3.1
ASMIs fall into two classes: direct and in-direct.
A behavioral model for a direct class ASMI is illustrated in
Figure 3-7. In the model, an event is represented as a short
duration (much less than 1 µs) positive pulse that is associ-
ated with a given Enable/Event pair n. The Enable/Event
pair is represented by a pair of simple “D” flip/flops that can
be set (write 1 to Q) or cleared (write 0 to Q) by software.
The EN bit can be written high or low, but the FLAG bit can
only be cleared. By GeodeLink architecture convention,
writing a 1 to a FLAG bit clears it; writing a 0 has no effect.
If the EN bit is 1, then the 0-to-1 transition of the event
pulse clocks a 1 into the SMI FLAG flip/flop.
All of the ASMI bits are ORed together to form the GLD
ASMI. The GLD ASMI is routed through the GLIU where it
is ORed with all other device ASMIs to form the CS5535
ASMI.
Event
[X]
Figure 3-7. Direct ASMI Behavioral Model
ASMI
+
Other ASMI
FLAG Bits
SMI MSR
FLAG Bit[n+1]
Bit[n]
D
D
EN
CI
CI
Q
Q
ASMI
[n+1]
Clear_By_Software
Set_By_Software
Clear_By_Software
GLD ASMI
(Continued)
68
A behavioral model for a in-direct class ASMI is illustrated
in Figure 3-8 on page 69. An event is represented as
before, but it is first applied to some type of Native Event
register. Generally, this is an IRQ status register of some
kind that records multiple IRQ sources. Alternatively, there
might be multiple independent Native Event registers that
are at some point ORed together to form a single Native
Event Summary Signal (NESS). In general, a NESS can
also be an IRQ signal routed to the PIC subsystem. Hence,
depending on operational needs, a NESS can be an IRQ or
ASMI.
The important point is that the NESS 0-to-1 transition
clocks a 1 into the SMI FLAG flip/flop. The event only in-
directly causes the SMI FLAG bit to be set. Further note
that the Event[X] and ASMI[n+1] are independently clear-
able. ASMI[n+1] can be cleared, while leaving NESS at a 1
state. After such clearing action with NESS high,
ASMI[n+1] will not set again. Alternatively, Event[X] could
be cleared without effecting the state of ASMI[n+1].
Lastly, it is possible to clear and set ASMI[n+1] while NESS
remains at a constant high state. Consider the following
sequence:
1)
2)
3)
4)
5)
6)
Note: Step 5 could also be performed between steps 2
The previous sequence is used when multiple events X, Y,
Z, etc. all OR to form a single NESS. The events are shar-
ing a single NESS. Under this arrangement, the following
Virtual System Architecture (VSA) software sequence
would be typical:
1)
2)
3)
4)
5)
6)
7)
Assume EN[n] is high.
Event[X] occurs and NESS makes a 0-to-1 transition
that sets ASMI[n+1].
Software clears ASMI[n+1] by writing a 1 to it.
NESS remains high because Event[X] has not been
cleared.
EN[n] is cleared to 0.
EN[n] is set to a 1 and causes ASMI[n+1] to be set
again.
Assume EN[n] is high.
Event[X] fires and causes a CS5535 ASMI.
VSA searches the GX2/CS5535 system looking for the
ASMI source and finds ASMI[n+1].
VSA clears EN[n] to 0 and begins to perform the
actions associated with Event[X].
While the “actions” are being taken, Event[Y] fires.
VSA
ASMI[n+1].
NESS remains high because Event[Y] has fired.
and 3 instead, yielding the same result. The
sequence of setting EN[n] to 0 followed by setting
EN[n] to 1 is called an Enable Toggle.
“actions”
include
clearing
Event[X]
Revision 0.8
and