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Interfacing A PS-2 Keyboard and VGA Monitor To Xilinx XC3S200 FPGA

This document discusses interfacing a PS-2 keyboard and VGA monitor to an XC3S200 FPGA. It describes the PS-2 keyboard port timing and serial communication protocol. Keyboard scan codes are transmitted as 11-bit frames over the data line synchronized to the clock line. The proposed architecture includes a PS-2 keyboard controller and VGA display controller to read the keyboard scan codes and output color and sync signals to the VGA monitor.

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Niranjan Sharma
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249 views14 pages

Interfacing A PS-2 Keyboard and VGA Monitor To Xilinx XC3S200 FPGA

This document discusses interfacing a PS-2 keyboard and VGA monitor to an XC3S200 FPGA. It describes the PS-2 keyboard port timing and serial communication protocol. Keyboard scan codes are transmitted as 11-bit frames over the data line synchronized to the clock line. The proposed architecture includes a PS-2 keyboard controller and VGA display controller to read the keyboard scan codes and output color and sync signals to the VGA monitor.

Uploaded by

Niranjan Sharma
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Interfacing a PS-2 Keyboard and VGA Monitor to Xilinx XC3S200 FPGA

Hardware Description Languages - MNE 2102

Project
Department of Microelectronics and Nanoelectronics

VGA Port

Department of Microelectronics and Nanoelectronics

VGA Port

Department of Microelectronics and Nanoelectronics

640 x 480 Mode VGA Timing

25 MHz

Department of Microelectronics and Nanoelectronics

PS-2 Keyboard Port

Department of Microelectronics and Nanoelectronics

PS/2 Timing

Department of Microelectronics and Nanoelectronics

Keyboard to FPGA Communication


The Data and Clock lines are both open collector. A resistor is connected between each line and +5V, so the idle state of the bus is high. When the keyboard wants to send information, it first checks the Clock line to make sure it's at a high logic level. If it's not, the FPGA is inhibiting communication and the device must buffer any to-be-sent data until the host releases Clock. The Clock line must be continuously high for at least 50 s before the device can begin to transmit its data.
Department of Microelectronics and Nanoelectronics

Keyboard to FPGA Communication


The keyboard use a serial protocol with 11-bit frames. These bits are:
1 start bit. This is always 0. 8 data bits, least significant bit first. 1 parity bit (odd parity). 1 stop bit. This is always 1.

Department of Microelectronics and Nanoelectronics

Keyboard to FPGA Communication


The keyboard writes a bit on the Data line when Clock is high, and it is read by the host when Clock is low.

Department of Microelectronics and Nanoelectronics

PS/2 Keyboard Scan Codes

Department of Microelectronics and Nanoelectronics

Example: 1D => W

start

parity bit scan code

Department of Microelectronics and Nanoelectronics

stop

Proposed Architecture

CLK_in reset PS2_CLK PS2_DATA read

scan_err scan_arv scan_code

CLK_in scan_code 50 MHz crystal

red_out green_out blue_out hs_out vs_out

Department of Microelectronics and Nanoelectronics

PS-Keyboard Controller
reset CLK_in PS2_CLK PS2_DATA read scan_arv scan_err Asynchronous reset Main synchronization clock signal Clock signal generated by the keyboard Signal on which serial data from the keyboard is transmitted to the FPGA This is an input which must be pulsed when the scan_code is read. This flag goes to 1 when a word has been received. Remains there until read is asserted and then goes low at the next clock cycle. This flag is set when the data received is incorrect (parity, stop) or when there is an overflow. This flag is automatically cleared when the reception of a new character begins. (8 bits) is the data word received from the keyboard

scan_code

Department of Microelectronics and Nanoelectronics

VGA Display Controller


CLK_in scan_code red_out green_out blue_out hs_out vs_out Main synchronization clock signal (8 bits) is the data word received from the keyboard Red Colour Enable Green Colour Enable Blue Colour Enable Horizontal sync signal Vertical sync signal

Department of Microelectronics and Nanoelectronics

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