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TPCE636 User Manual Issue 1.0.2
Page 64 of 104
7.9.4 Programming Hints LTC2323-16
The LTC2323-16 digital interface is a simple clocked SPI based interface.
This differential interface uses differential LVDS signals for serial data transfer. All LVDS signals need a
termination on the receiver side of the connection. For the SCK
±
an external resistor is implemented on the
TPMC636. The User FPGA inputs CLKOUT
±
, SDO1
±
and SDO2
±
of each ADC channel need an FPGA
internal termination. The corresponding constrains for the pin assignment, the I/O standard, termination and
slew rate is specified in Appendix A.
SCK+
SCK-
Kintex-7
CLKOUT-
SDO1+
SDO1-
SDO1+
SDO1-
CNV#
100R
LTC2323
Figure 7-8 : Digital ADC to FPGA Interface
A conversion is triggered by a negative edge on the CNV# line. The acquisition is done during the positive
phase of the CNV# signal. Following the FPGA drives the SCK clock, which then initiates the data transfer
from the ADC to the FPGA. The ADC then transmits the serial data SDO1 / SDO2 synchronous to CLKOUT.
The data sequence is MSB first and the LSB at least.
SDOx
CNV#
SCK
CLKOUT
B14
B15
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
acqusition
convertion and readout
acqusition
Figure 7-9 : Timing Diagram LTC2323-16
Note, that the one-cycle conversion latency has the result that the previous sample word is
transmitted first. That means, at the beginning of a burst sampling period the first conversion result
will be invalid.
For a detailed description of the LTC2323-16 interface and the LTC2323-16 function please use the data
sheet which describes the whole communication process and all special characteristics of the ADC.