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This version (14 Jan 2021 05:36) was approved by Robin Getz.The Previously approved version (16 Apr 2019 10:36) is available.Diff

Generic AXI DAC IP core

The following wiki page presents a generic framework, which is used to design and develop an AXI based IP core for interfacing a Digital to Analog Converter (DAC) device with a high speed serial (JESD204B) or source synchronous parallel interface (LVDS/CMOS). This is a generic framework, there can be minor differences on each and every IP, the user should study this wiki page along with the IP's wiki page.

The main role of this page to ease the understanding of each DAC IP, and to provide a base knowledge which can be used to develop new IPs for currently unsupported devices.

Any kind of feedback regarding the DAC IP architecture or the following document is highly appreciated and can be addressed through the FPGA Reference Designs community forum.

Architecture

The main function of an AXI DAC IP is to handle all the low level signalling, which is defined by the device's digital data interface, and to forward the received data from the DMA or any other data source to the device. Beside this functionality there are a few processing modules inside the data path of the core, which can be used for signal conditioning. All these processing modules are optional, the are enabled or disabled by setting the appropriate parameters. The following block diagram presents a generic AXI DAC IP cores data path.

Transmit PHY

The most important part of the core is the Transmit PHY module. This module contains all the IO primitive instantiations and all the control logic required to receive data from the device.

All the PHY modules follows the same naming convention: axi_<device_name>_if.v (e.g. axi_ad9467_if.v)

In some cases, when the IP supports multiple interface type, the name of the PHY module look like: axi_<device_name>_<interface_type>_if.v (e.g. axi_ad9361_lvds_if.v)

Currently the Transmit PHY supports two different transmit interface:

All these interfaces are supported on both Altera (Intel) and Xilinx devices.

This module is perfect choice for those, who wants a HDL logic for the device interface, with a minimal resource footprint.

(1) The transmit module contains just the Transport Layer of the JESD204B interface. Lower layers are implemented by other cores.

DAC channel

  • Data source multiplexer
  • IQ correction module

TODO: wiki page about each module TODO: describe the (Read) FIFO interface

DAC core

The DAC core is the top file of the IP core, the naming convention of this file is: axi_<device_name>.v . Here are instantiated all the internal module discussed above, and a wrapper module (up_axi), which converts the AXI interface into a more simplistic addressable, memory mapped interface, so called microprocessor interface or uP interface. This interface is used to interconnect the different memory mapped module pieces.

Signal and Interface Pins

A generic AXI DAC core have at least three different interfaces:

  • The physical data interface (LVDS or CMOS) or the JESD204B data interface from the link layer
  • Read FIFO interface for the transmit or source module (e.g. DMA)
  • AXI Slave Memory Mapped interface for register map access
Interface Pin Type Description
LVDS or CMOS TX interface
tx_clk_in_[p|n] clock input clock input (device's DCO)
tx_clk_out_[p|n] clock output clock output (device's DCI)
tx_data_out_[p|n] output[resolution-1:0] parallel data output (note that multiple parallel data buses can exist)
JESD TX interface
tx_clk clock input core clock or device clock (must be (line clock)/40)
tx_data output[DW-1:0] data input; DW=32*MAX_LANE_NO
Read FIFO interface
dac_clk clock output Interface's clock signal
dac_enable_0 output Enable signal for the first channel, asserted if channel is active
dac_valid_0 output Data valid signal for the first channel, to validate data on the bus
dac_data_0 input[DW-1:0] Data signal for the first channel
dac_enable_x output Enable signal for the channel x, asserted if channel is active
dac_valid_x output Data valid signal for the channel x, to validate data on the bus
dac_data_x input[DW-1:0] Data signal for the channel x
dac_dunf input Data underflow signal from the receiver or sink module (e.g DMA)
AXI Memory Map Slave
s_axi_* Standard AXI Slave Memory Map interface for register map access

Register Map

TODO: wiki page about the register map architecture

  • present the AXI Memory Mapped interface
  • talk about the UP_AXI wrapper and the simplified register interface
  • present read and write logic
  • present CDC circuits

The following block diagram presents the different register maps physical location in the core. These register maps are generic and can be found in each AXI DAC core.

The base and DAC common register map is implemented in the same verilog file. It contains registers which controls and monitors the overall core, like:

  • Reset bits
  • Attributes of the transmit interface module
  • DRP (Dynamic Reconfiguration Port) access for different IO resources (Clock Management Units, PLLs, Gigabit Transceivers etc.)
  • Status registers (PN Monitor status, frequency of the interface clock)
The DAC Common register map is implemented in the up_dac_common.v verilog file. To find the instantiation of this module search for up_dac_common inside the IP's directory.

The DAC Channel register map controls and monitors channel specific attributes. Each channel of the core has an individual channel register map. It contains all the registers, which are necessary to control and monitor the processing modules of the data path. For detailed description of the available processing modules see DAC channel section.

The DAC Channel register map is implemented in the up_dac_channel.v verilog file. To find the instantiation of this module search for up_dac_channel inside the IP's directory.

Typical Register Map base addresses

Base (common to all cores)

Click to expand regmap

DAC Common (axi_ad*)

Click to expand regmap

JESD TPL (up_tpl_common)

Click to expand regmap

DAC Channel (axi_ad*)

Click to expand regmap

IO Delay Control (axi_ad*)

Click to expand regmap

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resources/fpga/docs/axi_dac_ip.txt · Last modified: 14 Jan 2021 05:24 by Robin Getz