FMC-BB-4DA User Guide: RF Interfaces

The FMC-BB-4DA is built around two ​Analog Devices AD9116 devices. Each AD9116 provides two 12-bit, 125MSps DACs.

All digital signals from both AD9116 are tied to FMC I/O pins. The user's FPGA design is responsible for all control, clocking and data input to the DACs.

Data

The two AD9116's can be clocked at different frequencies by the user design. The digital sample interface for each AD9116 is a 12-bit DDR bus, with samples for the two DACs presented on opposite edges of the clock.

Clocking

Each AD9116 has one clock input. The input clock is used by both DACs in the IC. The sample rate of the two DACs in each AD9116 is equal to the input clock frequency. The two AD9116's on the FMC-BB-4DA can be clocked at different frequencies, if desired.

Control

The AD9116 has four digital control signals. These signals operate either as direct control lines or as an SPI interface. We use these signals in direct control mode (called "pin mode" in the AD9116 datasheet). User applications can instantiate an SPI controller and use this interface in SPI mode, if desired.

The function of the four control signals are listed in the table below. The default values listed here match those implemented in the fmc_bb_4da_bridge core.

Signal	AD9116 Pin	Default	Function
PINMD	35	1	Enables "pin mode" for the control interface, disables SPI register access
CLKMD	36	0	Determines phase relationship of data and DAC clocks
FORMAT	37	1	Sets data format (0: offset binary, 1: two's complement)
PWRDN	38	0	Powers down control (1: power off all circuits (except SPI) in the AD9116)