XC3S100E Datasheet, PDF (77/193 Pages) Xilinx, Inc – DC and Switching Characteristics

Functional Description
R
Spartan-3E FPGA
MOSI
FPGA-based ^DIN
SPI Master _CCLK
CSO_B
User-I/O
SPI Serial Flash PROM
+3.3V
DATA_IN
DATA_OUT
CLOCK
SELECT
User Data
MicroBlaze
Code
FPGA
Configuration
FFFFF
0
SPI Peripherals
• A/D Converter
DATA_IN
DATA_OUT
• D/A Converter
• CAN Controller
• Temperature Sensor
CLOCK
• Displays
SELECT
• Temperature Sensor
• Microcontroller
• ASSP
To other SPI slave peripherals
DS312-2_47_022205
Figure 53: Using the SPI Flash Interface After Configuration
Similarly, the SPI bus can be expanded to additional SPI
peripherals. Because SPI is a common industry-standard
interface, there are a variety of SPI-based peripherals avail-
able, including analog-to-digital (A/D) converters, digi-
tal-to-analog (D/A) converters, CAN controllers, and
temperature sensors.
The MOSI, DIN, and CCLK pins are common to all SPI
peripherals. Connect the select input on each additional SPI
peripheral to one of the FPGA user I/O pins. If HSWAP = 0
during configuration, the FPGA holds the select line High. If
HSWAP = 1, connect the select line to +3.3V via an external
4.7 kΩ pull-up resistor to avoid spurious read or write oper-
ations. After configuration, drive the select line Low to select
the desired SPI peripheral. Refer to the individual SPI
peripheral data sheet for specific interface and communica-
tion protocol requirements.
Daisy-Chaining
If the application requires multiple FPGAs with different con-
figurations, then configure the FPGAs using a daisy chain,
as shown in Figure 54. Use SPI Flash mode
(M[2:0] = <0:0:1>) for the FPGA connected to the Platform
Flash PROM and Slave Serial mode (M[2:0] = <1:1:1>) for
all other FPGAs in the daisy-chain. After the master
FPGA—the FPGA on the left in the diagram—finishes load-
ing its configuration data from the SPI Flash PROM, the
master device uses its DOUT output pin to supply data to
the next device in the daisy-chain, on the falling CCLK edge.
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DS312-2 (v1.1) March 21, 2005
Advance Product Specification