White Paper

Single-Resistor RSDS Solution for Cyclone II Devices

IntroductionThe reduced swing differential signaling (RSDS) interface is used in flat-panel displays to implement the data transfer between the timing controller and the column drivers. The Altera Cyclone II FPGA family is well suited to this interface due to its logic density, flexible I/O buffers, and low price. The Cyclone II device can implement the timing function and output the required RSDS signals to interface with the column driver.

This white paper explains how to implement the interface using a single external resistor. The single resistor solution makes the board design simple, less expensive, and more reliable. Altera's characterization of the single resistor RSDS solution was developed to meet today's RSDS speed requirements of 170 Mbps. This document covers the board-level circuit needed to create the correct signal levels according to RSDS specification and Quartus software support. Altera has verified this design through both simulation and board correlation.

RSDS SpecificationThe RSDS specification was developed by National Semiconductor Corporation for LDI (LVDS Display Interface), and is defined for use in chip-to-chip applications between the TCON (timing controller) and the column drivers on display panels. Characterization and simulations for Cyclone II devices were performed to meet National Semiconductor's RSDS Interface Specification. Table 1 shows these RSDS electrical characteristics.

Figures 1 and 2 show the RSDS receiver and transmitter signal waveforms, and explain the different electrical voltage levels involved in RSDS specification.

Figure 1. Receiver Input Signal Level Waveforms for RSDS

Table 1. RSDS Electrical Characteristics for Cyclone II Devices

Symbol Parameter Min Typical Max UnitsVCCIO I/O supply voltage 2.375 2.5 2.625 V

VOD Differential output voltage 100 200 600 mV

VOS Output offset voltage 0.5 1.2 1.5 V

VTH Differential threshold +/- 100 mV

Differential W aveform

Positive Channel (p) = VIH

Negative Channel (n) = VIL

Ground

VID

VCMOctober 2005, ver. 1.0 1

WP-C20905-1.0

VID

VID

p - n = 0 VVID (Peak to Peak)

Single-Resistor RSDS Solution for Cyclone II Devices Altera Corporation

Figure 2. Transmitter Output Signal Level Waveforms for RSDS

Cyclone II FPGAs support all three bus configuration types defined by the RSDS specification:

Type 1 - Multi-drop bus with double termination Type 2 - Multi-drop bus with single end termination Type 3 - Double multi-drop bus with single terminationMore information on RSDS bus configuration types can be found in the RSDS specification section of the National Semiconductor website.

Designing With RSDSCyclone II devices do not have differential drivers. To create the differential signal the device uses two adjacent I/Os as a differential pair along with an external on-board parallel resistor. The I/O bank in which the RSDS I/Os reside should be supplied with a 2.5-V power supply. (Refer to the software section on how to enable single resistor RSDS I/Os in Quartus development software.) To transmit an RSDS signal, an external resistor (RP) is connected in parallel between the two adjacent I/O pins on the board as shown in Figure 1. The recommended value of the resistor for all RSDS bus configurations is 100 (tolerance of 1%). Altera has verified this design through simulation and board correlation. A copy of the characterization data can be obtained by contacting Altera.

Figure 3. RSDS Resistor Network

Quartus Software SupportSupport for single resistors will be available in Quartus development software version 5.1. To assign single-resistor

Differential W aveform

Positive Channel (p) = VOH

Negative Channel (n) = VOL

Ground

VOD

VOD

VOD

VCM

p - n = 0 V

RP RL = 100

Copyright 2005 Altera Corporation. All rights reserved. Altera, The Programmable Solutions Company, the stylized Altera logo, specific devicedesignations, and all other words and logos that are identified as trademarks and/or service marks are, unless noted otherwise, the trademarks and servicemarks of Altera Corporation in the U.S. and other countries. All other product or service names are the property of their respective holders. Altera productsare protected under numerous U.S. and foreign patents and pending applications, maskwork rights, and copyrights. Altera warrants performance of itssemiconductor products to current specifications in accordance with Altera's standard warranty, but reserves the right to make changes to any products andservices at any time without notice. Altera assumes no responsibility or liability arising out of the application or use of any information, product, or servicedescribed herein except as expressly agreed to in writing by Altera Corporation. Altera customers are advised to obtain the latest version of device

101 Innovation DriveSan Jose, CA 95134(408) 544-7000

Altera Corporation Single-Resistor RSDS Solution for Cyclone II Devices

1. Select the pins to be assigned RSDS I/O standards and go to those pins within the Assignments section.

2. In the I/O standard option, select "simple RSDS" as shown in Figure 4.

3. Save and compile.

Figure 4. Assigning "Simple RSDS" I/O Standard

SummaryThis document describes how to implement single resistor RSDS I/Os in Altera's Cyclone II devices and the benefits of doing so. Cyclone II devices support multiple I/O standards such as LVDS, RSDS, and mini-LVDS typically used in flat panel display applications. Along with these flexible I/Os, the logic density, dedicated memory interfaces, and internal memory of these devices makes them an ideal choice for implementing the timing controller functionality. Altera also offers design examples and reference design boards to implement and prototype most of the display interfaces.

Additional Resources National Semiconductors RSDS Specification:

www.national.com/appinfo/fpd/0,2132,943,00.html3

specifications before relying on any published information and before placing orders for products or services.http://www.altera.com

IntroductionRSDS SpecificationDesigning With RSDSQuartus Software SupportSummaryAdditional Resources