VSC7177 データシートの表示（PDF） - Maxim Integrated
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VSC7177 Datasheet PDF : 24 Pages
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VSC7177
Data Sheet
FUNCTIONAL DESCRIPTIONS
Modes of Operation
The VSC7177 has two modes of operation: sideband port selection and protocol port selection. Each mode
corresponds to a different method of configuring port connectivity. Only one of the operating modes is active at any
time in the VSC7177. Sideband-based port connectivity is controlled externally using the I/O pins of the device itself.
Protocol-based connectivity is implemented as defined in the Serial ATA II: Port Selector 1.0 specification.
Selecting Operating Modes
There are two types of sideband-based port selections: Edge-sensitive and level-sensitive. Rising-edge transitions on
the PORTSEL0 and PORTSEL1 inputs cause the corresponding port to become active when in edge-sensitive
sideband-based selection mode. Edge-sensitive sideband port selection is enabled when MODE1 is HIGH.
PORTSEL0 determines the active port in level-sensitive sideband-based mode. Level-sensitive sideband port
selection is enabled when MODE1 is LOW and PORTSEL1 is LOW.
Setting MODE1 LOW and PORTSEL1 HIGH in the VSC7177 allows the protocol-based Serial ATA II port selection
and test modes to be enabled. PORTSEL0 and MODE0 are used to select these operating modes shown in Table 1.
The functionality of the various operating modes is described in the following sections.
The setting of PORTSEL1 constitutes one of the primary differences between the VSC7177 and the VSC7173 and the
VSC7175. In the VSC7177, PORTSEL1 must be set LOW in level-sensitive sideband mode. The setting of
PORTSEL1 has no effect on the operation of the VSC7173 and the VSC7175 in level-sensitive mode (it is a “don’t
care”). For a complete list of differences between the VSC7177 and the VSC7173 and the VSC7175, see “Pinout
Differences Between VSC7177 and VSC7173/VSC7175,” page 13.
Table 1 shows how to configure the VSC7177 to operate in any of the various available modes.
Table 1. Operating Modes
Modes of Operation
Edge-sensitive sideband port selection
Level-sensitive sideband port selection
Reserved
Test modes
Protocol-based Serial ATA II port
selection
Test modes
MODE1
1
0
0
0
0
0
Configuration Pins
MODE0
PORTSEL0
PORTSEL1
Select output mode of
unconnected port
Select output mode of
unconnected port
↑ edge makes port 0 ↑ edge makes port 1
active
active
Selects connected port
0 (1)
0
0
1
0
1
1
1
0
1
1
1
1
X = don’t care; ↑ = rising.
1. PORTSEL1 must equal VSS in level-sensitive sideband-based port selection mode. (The VSC7173 and the VSC7175 allow
PORTSEL1 = X.)
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Revision 4.2
July 29, 2005
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