Evaluation boards
There is no shortage of FPGA evaluation boards available for us to purchase. One company that makes very affordable boards is Digilent. There are several nice features that its boards tend to include, but one of the best is that they have a built-in USB-to-UART controller that Xilinx Vivado recognizes as a programming cable. This makes configuring the device painless. The recommended boards also have the added advantage of being powered over this same USB cable.
The Nexys A7 is the recommended board for this book. It has all the devices we’ll target over the course of the book.
Nexys A7 100T (or 50T)
Figure 1.11 below is a picture of the Nexys A7 board. There are two variants of the board at the time of writing, the 100T variant and the 50T variant. The difference is only the size of the device installed on the board.
Figure 1.11: Digilent Nexys A7 board
The board features are as follows:
- Artix-7 XC7A100T or 50T
- 450+ MHz operation
- 128 MB DDR2
- Serial flash
- Built-in USB UART for downloading images and ChipScope debugging
- MicroSD card reader
- 10/100 Ethernet PHY
- PWM audio output/microphone input
- Temperature sensor
- 3-axis accelerometer
- 16 switches
- 16 LEDs
- 5 push buttons
- Two 3-color LEDs
- Two 4-digit 7-segment displays
- USB host device support
- Five PMOD (one XADC)
Let’s take a look at the breakdown of the two devices that the Nexys board can be ordered with:
|
Device |
XC7A100T-1CSG324C |
XC7A50T-1CSG324C |
|
Logic slices |
15,850 |
8,150 |
|
BRAM (Kbits) |
4,860 |
2,700 |
|
Clock management tiles |
6 |
5 |
|
DSP |
240 |
120 |
Table 1.3: Breakdown of the devices
One benefit of choosing the XC7A100T is the additional RAM. Especially at the start, you may find yourself relying on chip debugging using ChipScope, and the additional RAM will allow for additional storage for wider busses or longer capture times. We’ll discuss ChipScope in the later chapters.
