Digilent 410-087P-KIT - Manual (Page 67)

Spartan-3E Starter Kit Board User Guide www.xilinx.com 67
UG230 (v1.0) March 9, 2006
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Chapter 9
Digital to Analog Converter (DAC)
The Spartan-3E Starter Kit board includes an SPI-compatible, four-channel, serial Digital-
to-Analog Converter (DAC). The DAC device is a Linear Technology LTC2624 quad DAC
with 12-bit unsigned resolution. The four outputs from the DAC appear on the J5 header,
which uses the Digilent 6-pin
Peripheral Module format. The DAC and the header are
located immediately above the Ethernet RJ-45 connector, as shown in Figure 9-1 .
SPI Communication
As shown in Figure 9-2 , the FPGA uses a Serial Peripheral Interface (SPI) to communicate
digital values to each of the four DAC channels. The SPI bus is a full-duplex, synchronous,
character-oriented channel employing a simple four-wire interface. A bus master—the
FPGA in this example—drives the bus clock signal (SPI_SCK) and transmits serial data
(SPI_MOSI) to the selected bus slave—the DAC in this example. At the same time, the bus
slave provides serial data (SPI_MISO) back to the bus master.
Figure 9-1: Digital-to-Analog Converter and Associated Header
6-pin DAC Header (J5)
Linear Tech LTC2624 Quad DAC
SPI_MOSI: (T4)
SPI_MISO: (N10)
SPI_SCK: (U16)
DAC_CS: (N8)
DAC_CLR: (P8)
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