Implemented proper address forwarding for read requests to the FIFO interface, ensuring correct functionality during data read operations. Documented the usage procedures for data reads and writes and refined the history and timing diagrams in the associated documentation for clarity. This update includes reorganizing comments for better readability and updating signal controls to synchronize address handling with data output.
Included new Logic Analyzer Captures section in README and created a corresponding markdown file with waveform images for various EPP cycles. This provides visual aids for better understanding the timing and behavior of EPP transactions.
* Enhanced edge detection in DEPP
Updated the DEPP VHDL component with clearer comment annotations and modified edge detection logic for address and data enable signals. Additionally, refined the main state machine by explicitly adding states for edge waiting periods and defining behaviors for each state, specifically regarding the handling of output FIFO signals and cycle initiation. Updated the edge detection mechanism within the address and data processing workflows, improving cycle handling for idle, address, and data states to better signal the transitions and manage the bus as well as the request and write enable signals.
* Implement FIFO compatible interface and update waveforms
Enhanced DEPP documentation and diagrams to reflect a transition to FIFO compatible interfaces for data traffic efficiency. Updated waveforms depict the revised cycle timings for data/address commands and address acknowledgment, ensuring clarity on the implemented protocol changes.
* Refine DEPP VHDL port naming for clarity
Updated the DEPP VHDL entity's port naming convention to enhance readability and consistency across data and address lines. Introduced clear "Fifo" and "AddressOut" prefixes as per FIFO compatible interfaces, replacing generic data and address signal names. This renaming also strengthens the association between ports and their respective data flow. Additional changes include:
- Replaced 'DataAviable' with a negated 'DataInFifo_EmptyFlag' for immediate data availability check.
- Streamlined write enable signals alignment with the new naming convention.
- Redesigned read-enable logic to minimize latency in 'RequestActive' mode by directly relaying the 'DataInFifo_DataAviable' status.
- Simplified and restructured bus wait management states to reflect the updated port names and signal handling improvements.
- Removed obsolete comments and updated documentation to accurately reflect the current interface functionality and structure.
* Enhanced DEPP module docs and waveform references
- Updated the DEPP module documentation to improve clarity and readability.
- Refactoring included renaming of waveform files for consistency and eliminating unnecessary whitespace.
- Revised virtual bus interface descriptions for better accuracy and cleared up the ambiguity in port names and their corresponding descriptions.
- Streamlined the ports and signals tables to enhance document structure and coherence.
- Modified the state machine SVG file for an up-to-date representation of the module design.
- Integrated additional waveform diagrams to detail the EPP (Enhanced Parallel Port) bus cycles within the documentation.
* Optimized EPP state machine timing
Refactored the EPP (Enhanced Parallel Port) VHDL state machine to streamline the signal handling for different operating states. This optimization includes removing redundant assignments to the `DEPP_Wait` signal in intermediary states and ensuring it is only held high for a minimum of one cycle where necessary. These modifications enhance the clarity of state transitions and may improve the system's timing performance, particularly for the start of read, write, and address cycles.
Additionally, the documentation is updated to include measured data rates, aiding in setting performance expectations.
* Enhanced UCF readability and added LA constraints
Reformatted the pin constraints section in Nexys2Test.ucf to improve readability, adding descriptive comments for RST, DataOutFullFlag, and RequestFullFlag signals. Removed unnecessary net constraints related to DEPP interface signals. Extended the UCF to include configuration for the Logic Analyzer (LA), specifying appropriate locations and providing comments linking net names to their corresponding physical connectors.
* Refactor signal handling and add Logic Analyzer output
Updated the Nexys2Test VHDL entity to streamline signal handling and add support for a Logic Analyzer interface. Removed commented-out attributes for virtual bus and related signals, which simplifies the interface section. Introduced new outputs for the Logic Analyzer to monitor various signals such as address, data enable, write enable, and wait signals, which improves debug and testing capabilities. In the architecture, redundant process handling DEPP_Wait has been removed to reduce complexity, and DEPP_Bus is now directly assigned. Updated the main process to simplify LED assignments and fixed an incorrect value for DataInFifo_EmptyFlag, enhancing signal accuracy and conforming to expected logic levels. These changes contribute to a more maintainable and understandable codebase.
* Update EPP documentation with data rate and refreshed diagrams
- Added the measured data transfer rate to the DEPP documentation.
- Replaced EPP bus waveform diagrams with updated versions.
- Resized and restructured the DEPP FSM SVG for better legibility, including adjustments to cluster dimensions, node positions, edges, and transitions.
- Renamed waveform SVG files for a consistent naming convention.
* Added logic analyzer capture visuals for documentation
* Added MIT License and enhanced README for DEPP module
Implemented an MIT License file and updated the README to provide comprehensive documentation for the VHDL Module designed for the Digilent Asynchronous Parallel Port Interface. The README now includes an overview of the module's purpose, features such as the measured data rate, visual diagrams for bus cycles, a detailed port definition table, module dependencies, contribution guidelines, licensing information, and acknowledgments, improving clarity and usability for end-users and contributors.
Co-authored-by: Max P <Mail@MPassarello.de>
Co-committed-by: Max P <Mail@MPassarello.de>
Introduced comprehensive documentation for the Digilent EPP (DEPP) interface, including its description, generics, ports, signals, types, and functions. Accompanying waveform diagrams for EPP Address Write were also included to illustrate the timing behavior and control signals during operations. This enhanced documentation will aid in understanding and utilizing the DEPP interface on Digilent FPGA boards.
