Digilent 410-274P-KIT - Manual (Page 22)

Nexys4™ FPGA Board Reference Manual
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Page 22 of 29
XADC core is controlled and accessed from a user design via the Dynamic Reconfiguration Port (DRP). The DRP also
provides access to voltage monitors that are present on each of the FPGA’s power rails, and a temperature sensor
that is internal to the FPGA. For more information on using the XADC core, refer to the Xilinx document titled “7
Series FPGAs and Zynq-7000 All Programmable SoC XADC Dual 12-Bit 1 MSPS Analog-to-Digital Converter.”
11 MicroSD Slot
The Nexys4 provides a microSD slot for both FPGA configuration and user access. The on-board Auxiliary Function
microcontroller shares the SD card bus with the FPGA. Before the FPGA is configured the microcontroller must
have access to the SD card via a SPI interface. Once a bit file is downloaded to the FPGA (from any source), the
microcontroller power cycles the SD slot and relinquishes control of the bus. This enables any SD card in the slot to
reset its internal state machines and boot up in SD native bus mode. All of the SD pins on the FPGA are wired to
support full SD speeds in native interface mode, as shown in Fig 21. The SPI interface is also available, if needed.
Once control over the SD bus is passed from the microcontroller to the FPGA, the SD_RESET signal needs to be
actively driven low by the FPGA to power the microSD card slot. For information on implementing an SD card
controller, refer to the SD card specification available at
www.sdcard.org .
Artix-7
A1
SD MICRO (J1)
VDD
DAT2
DAT1
CMD
CLK
DAT3
DAT0
CARD_DETECT
3.3V
SD_RESET
C2
D2
B1
C1
E1
F1
E2
12 Temperature Sensor
The Nexys4 includes an Analog Device ADT7420 temperature sensor. The sensor provides up to 16-bit resolution
with a typical accuracy better than 0.25 degrees Celsius. The interface between the temperature sensor and FPGA
is shown in Fig 22.
Artix 7 ADT7420
SDA
TMP_INT
TMP_CT
G16
D14
C14
SCL: I2C Serial Clock
SDA: I2C Serial Data
TMP_INT: Over-temperature and Under-temperature Indicator
F16 SCL
TMP_CT: Critical Over-temperature Indicator
Figure 21. Artix-7 microSD card connector interface (PIC24 connections not shown)
Figure 22. Temperature Sensor interface