Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
2000-07-14
2001-05-22
Etienne, Ario (Department: 2155)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S120000, C710S062000, C710S106000
Reexamination Certificate
active
06237056
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and method for high speed data transfer between PCB boards using ribbon cable.
2. Description of the Prior Art
There are several standards for ribbon cable interconnection known today. Three of the most advanced systems are Ultra ATA-66, ULTRA-2 SCSI and Wide ULTRA-2 SCSI. The Ultra ATA-66 standard allows data transfer at up to 66.6 MB/s burst data transfer rate at 33 MHz clock rate over 80 conductor wire using 40 signal and 40 interleaving ground conductors with 40 receptacle connectors. The ULTRA-2 SCSI and Wide ULTRA-2 SCSI allow burst data transmission of 40 and 80 MB/s at 40 MHz. with 8 bit and 16 bit buses respectively. ULTRA-3 SCSI promises double the Wide ULTRA-2 SCSI rates. However, the ULTRA-2 SCSI and ULTRA-3 SCSI systems require the use of twisted pair ribbon cables to support Low Voltage Differential where each signal is sent over two wires. Also the SCSI systems require complex active terminators and utilize data verification techniques such as CRC, which have substantial overhead and which limit the techniques where direct isochronous transfer is required.
High frequency board-to-board data transmission by ribbon cable is limited by issues of signal integrity including the following: a. driver characteristics such as slew rates, propagation delay and signal reflection; b. transmission line effects such as signal reflection impact, termination methodology, incident wave switching, load configurations, connectors, and ribbon cables; c. receiver capabilities, such as thresholds, signal skews, setup/hold times, and loading; and d. cross talk, involving the ribbon cable, signal pin-out, PCB traces, and EMI considerations. All of these factors make it uncertain whether a high speed data transmission over a given ribbon cable connection can maintain data integrity.
Many data transfer systems require both high speed and high bandwidth transfer. One particular system is high performance video transfer. The Video Electronics Standards Association (VESA) has recently adopted Version 2.0 of a Video Interface Port (VIP) Standard, which is a dedicated physical connection between a graphics adapter (a VIP master) and video devices such as MPEG-2 or HDTV decoders, video digitizers, video encoders, etc. (a VIP slave). Such high performance video transfer systems as VIP require reliable data transfer, which is isochronous (real time) and very high bandwidth (VIP 2.0 requires 150 MB/s transfer rate). Because of the limitations on reliability of high speed ribbon cable connections VESA did not adopt a ribbon cable implementation of its VIP 2.0 standard which operates with up to a clock rate of 80 MHz, and contemplates that the standard will be implemented by both master and slave mounted on a single board or a mother-daughter board arrangement. The earlier VIP version 1.1, which operated at 33 MHz included a ribbon cable transfer option. The single board requirement of VIP 2.0 is a significant limitation, since graphic controllers and video devices are typically manufactured by different manufacturers. The objective of the VIP Standard was to assure that devices manufactured by different parties could interface seamlessly. This objective is substantially compromised by the single board requirement.
Other PC based systems for real-time video transfer are not adequate for connecting VIP 2.0 slaves and masters. IEEE 1394 (known as Fire Wire) is isochronous but does not provide high enough transfer rates, USB is likewise too slow for high performance video. Fast PC bus structures such as PCI and AGP are asynchronous buses and cannot provide the needed direct isochronous interconnect.
There is a need for a reliable board-to-board data transfer system for transfer of data above 40 MHz based on readily available and inexpensive components comprising single-ended nbbon cable and connectors, whereby high speed data generated on a slave board constructed according to the system can reliably transfer the data to a master constructed according to the system by a ribbon cable of the system without the signal integrity reliability issues.
There is a need for an inexpensive and reliable system for direct linkage of VESA VIP 2.0 master and slave devices mounted on different boards.
There is a need for an inexpensive and reliable system for direct ribbon cable linkage of VESA VIP 2.0 master and slave devices mounted on different boards such that a board containing a slave of the system will reliably and isochronously link with a master of the system by a cable of the system.
There is a need for a reliable method for data transfer between boards at greater than 40 MHz using inexpensive and readily available single-ended ribbon cable.
SUMMARY OF THE INVENTION
One embodiment of the invention is a system for high speed board-to-board data transfer at between 40 and 80 MHz, between a slave device and a master device by a single-ended ribbon cable. A slave device according to the invention comprises a plurality of high speed primary drivers providing signals at from 40 to 80 MHz mounted on a slave printed circuit board. One of the signals should be a clock signal. The drivers are usually output circuits on an IC chip driving an output pin on the chip, but may also be external drivers mounted on the board. Each driver is connected to a ribbon cable connector pin mounted on the board by a primary driver trace line and has a series termination resistor between the driver and the ribbon connector pin. There can also be an optional set of secondary high speed drivers on the slave board also generating 40 to 80 MHz signals. Each secondary driver is connected to the corresponding primary trace line by a secondary trace line.
A master device according to the invention comprises a plurality of ribbon cable connector pins mounted on a master printed circuit board, a plurality of primary receivers one corresponding to each high speed transfer driver, and a plurality of primary trace lines connecting the cable connector pins on the master board and each of the primary receivers. Generally the receivers are input circuits on an IC chip receiving an input signal at an IC pin. The master board can also have a plurality of secondary receivers each connected to a primary trace line by a stub trace.
A ribbon cable according to the invention is a single-ended flat ribbon cable with a connector at each end. The cable preferably uses a ground-signal ground configuration. A preferred 40 pin cable of this type is an Ultra ATA cable with two Primary Drive Connectors. This type of cable is made with 80 conductor cable where 40 of the interleaving conductors are connected to a common ground and the 40 remaining conductors are connected to pin receptacles. An alternative cable would be to use cable and connectors with at least twice as many conductors as there are pins on the board and to ground alternate pins.
A preferred slave device comprises a VESA VIP 2.0 compliant slave. A VIP 2.0 slave supporting 8 bit video mode has 40 ribbon cable connector pins on the slave board corresponding to the 40 pins specified for the VIP 2.0 slave in 8 bit mode, while an VIP 2.0 slave supporting 10 bit extended video mode requires 50 ribbon cable connector pins corresponding to the 50 pins specified for a VIP 2.0 slave supporting 10 bit extended graphics. The cable connector pins include pins connected to primary transfer drivers and optional secondary drivers, other slower speed drivers such as those corresponding to the VIP host bus, and pins which are grounded.
A preferred master device is comprises a VESA VIP 2.0 compliant master. A VIP 2.0 master may support 8 bit video mode or 10 bit extended video mode corresponding to the options available for a VIP 2.0 slave and have either 40 or 50 pins corresponding to those of a VIP 2.0 slave.
A preferred ribbon cable for connecting 40 pin devices or 40 pins of 50 pin devices is an Ultra ATA cable with two Ultra ATA Primary Drive Connectors. A preferred ribbon cable for connecting the remaining 10 pins of a
Burnham James
Lam Chris
Etienne Ario
Lebowitz Howard E.
Videon, Inc.
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