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en:verilog:uart:readme [2014/11/09 09:08] alex [uart_rx module] |
en:verilog:uart:readme [2014/11/09 09:27] alex [Signals and Parameters] |
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| ==== Source Files ==== | ==== Source Files ==== | ||
| - | * ''rtl/uart.v'' - Wrapper for complete UART | + | <code> |
| - | * ''rtl/uart_rx.v'' - UART receiver implementation | + | rtl/uart.v : Wrapper for complete UART |
| - | * ''rtl/uart_tx.v'' - UART transmitter implementation | + | rtl/uart_rx.v : UART receiver implementation |
| + | rtl/uart_tx.v : UART transmitter implementation | ||
| + | </code> | ||
| - | ==== uart module ==== | + | ===== uart module ===== |
| - | * Parameters | + | ==== Signals and Parameters ==== |
| - | * ''parameter DATA_WIDTH = 8'' - define width of data bus and transferred words in bits | + | |
| - | * Clock and reset | + | <code> |
| - | * ''input wire clk'' - clock input | + | Parameters |
| - | * ''input wire rst'' - reset input | + | parameter DATA_WIDTH = 8 - define width of data bus and transferred words in bits |
| + | Clock and reset | ||
| + | input wire clk - clock input | ||
| + | input wire rst - reset input | ||
| * AXI Stream Interface (TX) | * AXI Stream Interface (TX) | ||
| * ''input wire [DATA_WIDTH-1:0] input_axis_tdata'' - data input | * ''input wire [DATA_WIDTH-1:0] input_axis_tdata'' - data input | ||
| Line 38: | Line 43: | ||
| * Configuration | * Configuration | ||
| * ''input wire [15:0] prescale'' - BAUD rate prescale value | * ''input wire [15:0] prescale'' - BAUD rate prescale value | ||
| + | </code> | ||
| + | |||
| + | ==== Description ==== | ||
| The ''uart'' module is simply a wrapper around the ''uart_rx'' and ''uart_tx'' modules. | The ''uart'' module is simply a wrapper around the ''uart_rx'' and ''uart_tx'' modules. | ||
| - | ==== ''uart_rx'' module ==== | + | ===== uart_rx module ===== |
| - | === Signals and Parameters === | + | ==== Signals and Parameters ==== |
| * Parameters | * Parameters | ||
| Line 63: | Line 71: | ||
| * ''input wire [15:0] prescale'' - BAUD rate prescale value | * ''input wire [15:0] prescale'' - BAUD rate prescale value | ||
| - | === Description === | + | ==== Description ==== |
| The ''uart_rx'' module implements the UART receive function. Bits received over the ''rxd'' pin are decoded and output on the AXI Stream interface. The baud rate is determined by the ''prescale'' setting, which should be set to Fclk / (baud * 8). ''prescale'' is a port and not a parameter so it can be changed at run time if necessary. The ''uart_rx'' module also generates frame and overrun error signals. The ''frame_error'' signal indicates that the stop bit was not received correctly, while the ''overrun_error'' signal indicates that a byte was received before the previous one was read, causing the older data byte to be overwritten. | The ''uart_rx'' module implements the UART receive function. Bits received over the ''rxd'' pin are decoded and output on the AXI Stream interface. The baud rate is determined by the ''prescale'' setting, which should be set to Fclk / (baud * 8). ''prescale'' is a port and not a parameter so it can be changed at run time if necessary. The ''uart_rx'' module also generates frame and overrun error signals. The ''frame_error'' signal indicates that the stop bit was not received correctly, while the ''overrun_error'' signal indicates that a byte was received before the previous one was read, causing the older data byte to be overwritten. | ||
| - | ==== uart_tx module ==== | + | ===== uart_tx module ===== |
| + | |||
| + | ==== Signals and Parameters ==== | ||
| * Parameters | * Parameters | ||
| Line 85: | Line 95: | ||
| * ''input wire [15:0] prescale'' - BAUD rate prescale value | * ''input wire [15:0] prescale'' - BAUD rate prescale value | ||
| - | ==== AXI interface ==== | + | ===== AXI interface ===== |
| The main interface to the user design is an AXI4-Stream interface that consists of the tdata, tvalid, and tready signals. tready flows in the opposite direction. tdata is considered valid when tvalid is high. The destination will accept data only when tready is high. Data is transferred from the source to the destination only when both tvalid and tready are high, otherwise the bus is stalled. | The main interface to the user design is an AXI4-Stream interface that consists of the tdata, tvalid, and tready signals. tready flows in the opposite direction. tdata is considered valid when tvalid is high. The destination will accept data only when tready is high. Data is transferred from the source to the destination only when both tvalid and tready are high, otherwise the bus is stalled. | ||
| - | === AXI Stream Interface Example === | + | ==== AXI Stream Interface Example ==== |
| two byte transfer with sink pause after each byte | two byte transfer with sink pause after each byte | ||