GS6150 Datasheet, PDF (30/64 Pages) Gennum Corporation – Automatic or Manual Rate Selection

Word portion for read operations to the device. This allows multiple devices to be
connected in Loop-Through configuration.
For read operations, the SDOUT pin is used to output data read from an internal
Configuration and Status Register (CSR) when CS is LOW. Data is shifted out of the
device on the falling edge of SCLK, so that it can be read by the host processor or other
downstream connected device on the subsequent SCLK rising edge.
4.11.3.1 GSPI Link Disable Operation
It is possible to disable the direct SDIN to SDOUT (Loop-Through) connection by writing
a value of 1 to the GSPI_LINK_DISABLE bit in REGISTER_0. When disabled, any data
appearing at the SDIN pin will not appear at the SDOUT pin and the SDOUT pin is HIGH.
Note: Disabling the Loop-Through operation is temporarily required when initializing
the Unit Address for up to 32 connected devices.
The time required to enable/disable the Loop-Through operation from assertion of the
register bit is less than the GSPI configuration command delay as defined by the
parameter t_{cmd_GSPI_config} (5 SCLK cycles).
Table 4-6: GSPI_LINK_DISABLE Bit Operation
Bit State
0
1
Description
SDIN pin is looped through to the SDOUT pin
Data appearing at SDIN does not appear at SDOUT, and SDOUT pin is HIGH.
SDIN pin
Configuration and
Status Register
GSPI_LINK
_DISABLE
BUS_THROUGH
SDOUT pin
High-Z
CS pin
Figure 4-6: GSPI_LINK_DISABLE Operation
4.11.3.2 GSPI Bus-Through Operation
Using GSPI Bus-Through operation, the GS6150 can share a common PCB trace with
other GSPI devices for SDOUT output.
When configured for Bus-Through operation, by setting GSPI_BUS_THROUGH_ENABLE
bit to 1, the SDOUT pin will be high-impedance when the CS pin is HIGH.
When the CS pin is LOW, the SDOUT pin will be driven and will follow regular read and
write operation as described in Section 4.11.3.
GS6150
Final Data Sheet
PDS-060127
Rev.2
March 2015
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