GS3140 Datasheet, PDF (22/40 Pages) Semtech Corporation – Multi-Rate Adaptive 3G SDI Equalizer

4.11.4 SCLK Pin
The SCLK pin is the GSPI serial data shift clock input to the device, and must be provided
by the host processor.
Serial data is clocked into the GS3140 SDIN pin on the rising edge of SCLK. Serial data is
clocked out of the device from the SDOUT pin on the falling edge of SCLK (read
operation). SCLK is ignored when CS is HIGH.
The maximum interface clock rate is 32MHz.
4.11.5 Command Word Description
All GSPI accesses are a minimum of 32 bits in length (a 16-bit Command Word followed
by a 16-bit Data Word) and the start of each access is indicated by the high-to-low
transition of the chip select (CS) pin of the GS3140.
The format of the Command Word and Data Words are shown in Figure 4-6.
Data received immediately following this high-to-low transition will be interpreted as a
new Command Word.
4.11.5.1 R/W bit - B15 Command Word
This bit indicates a read or write operation.
When R/W is set to 1, a read operation is indicated, and data is read from the register
specified by the ADDRESS field of the Command Word.
When R/W is set to 0, a write operation is indicated, and data specified in the Data Word
is written to the register specified by the ADDRESS field of the Command Word.
4.11.5.2 B'CAST ALL - B14 Command Word
This bit is used in write operations to configure all devices connected in Loop-Through
and Bus-Through configuration with a single command.
When B’CAST ALL is set to 1, the following Data Word (AUTOINC = 0) or Data Words
(AUTOINC = 1) are written to the register specified by the ADDRESS field of the
Command Word (and subsequent addresses when AUTOINC = 1), regardless of the
setting of the UNIT ADDRESS(es).
When B’CAST ALL is set to 0, a normal write operation is indicated. Only those devices
that have a Unit Address matching the UNIT ADDRESS field of the Command Word write
the Data Word to the register specified by the ADDRESS field of the Command Word.
B’CAST ALL must be set to 0 for read operations.
4.11.5.3 EMEM - B13 Command Word
The EMEM bit should be set to 0 when accessing GS3140. Accesses to other devices (Unit
Address field in the Command Word does not match the DEVICE_UNIT_ADDRESS in
HOST_CONF_REG_0) with EMEM bit set to 1 are allowed.
GS3140
Final Data Sheet
PDS-060939
Rev.1
May 2015
www.semtech.com
22 of 40
Semtech
Proprietary & Confidential