Getting Started Guide for LX9 and Nexys3 User Manual

Analog Essentials

Getting Started Guide

For LX9 and Nexys-3

Appendix A: Project Notes

1. Each active Pmod port has a dedicated I

C port, SPI port UART and octal GPIO. These communications

peripherals are multiplexed to the physical ports via an HDL designed multiplexer. (Refer to the diagram in the

Typical System Architecture section.) An example of this can be seen in the maximPMOD.c file at about the

midpoint, as shown in the clip below.

Also, note that all 4 Pmod ports on the Nexys-3 board are driven in this manner. However, due to gate count

limitation in the LX9, only one of its Pmod ports is actively driven by this configuration.

2. The functions in maximDeviceSpecificUtilities.c are used to access the major functionality provided by the

Maxim ICs. In general, these functions return an integer value (TRUE/FALSE) that describes whether or not the

function successfully completed. Although it is not required to check this return value, it is good programming

practice to do so.

3. Functions will typically require a peripheral port address. These ports are assigned sequentially from the sets of

C, SPI, UART and GPIO peripherals in the design, and are named from ports 0..3. (Again, the Nexys-3 design

includes 4 ports and the LX9 design includes one port.) Examples include:

a. XPAR_IIC_0_BASEADDR, XPAR_IIC_1_BASEADDR, XPAR_IIC_2_BASEADDR, etc.

b. XPAR_SPI_0_BASEADDR, XPAR_SPI_1_BASEADDR, etc

c. XPAR_AXI_UARTLITE_0_BASEADDR, XPAR_AXI_UARTLITE_0_BASEADDR, etc

4. GPIO calls receive a pointer to a Xilinx XGpio instance

a. XGpio portA;

b. XGpio_Initialize(&portA, XPAR_AXI_GPIO_0_DEVICE_ID);

Since the functions return TRUE/FALSE as a pass/fail indication, when the functions return a value, it is passed back to

the calling function via a pointer.