GS3140 Datasheet, PDF (20/40 Pages) Semtech Corporation – Multi-Rate Adaptive 3G SDI Equalizer

4.11.2 SDIN Pin
The SDIN pin is the GSPI serial data input pin of the GS3140.
16-bit Command and Data Words from the host processor or from the SDOUT pin of
other devices are shifted into the device on the rising edge of SCLK when the CS pin is
low.
4.11.3 SDOUT Pin
The SDOUT pin is the GSPI serial data output of the GS3140.
All data transfers out of the GS3140 to the host processor or to the SDIN pin of other
connected devices occur from this pin.
By default at power up or after system reset, the SDOUT pin provides a non-clocked path
directly from the SDIN pin, regardless of the CS pin state, except during the GSPI Data
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 HOST_CONF_REG_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} (4 SCLK cycles).
Table 4-4: 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.
GS3140
Final Data Sheet
PDS-060939
Rev.1
May 2015
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