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LOSTCIRCUITS		SHORTCUTS: IDE Cables: Wired RF Transmitters UDMA 33 vs UATA Cables Mechanical and RF Properties Real Cables Real World System Problems Tips and Conclusion Any Comments? Cheetahs and Cudas on the web
ATA Not-So-FAQs    Or: Why Ribbon Cables are unsuitable for RF transmission of data
(Article by snn47, March 17, 2003)          -.. ..-. ..... .--. -.--

The following is going to contain a substantial amount of technical details, those not interested please skip the section and jump to the preliminary conclusions.

• Signal-frequency/-duration, -voltage-level, -rise- and decay-time as well as -timing.
• Physical dimensions and material of cable and connector and wire. The conductor and insulation material with the physical dimensions define the velocity factor of the RF-propagation properties (For example, the RF-impedance difference between 40/80-wire flat-cable?)
• maximum allowable length (18"), location of the 3rd slave-connector
• what does an increase from ATA-33 to ATA66 or higher mean in signal-clock in MHz that need to be transmitted via the parallel-wire?

HW-differences in connector and cable 40- vs. 80-wire-flat-ribbon-cable

ATA 33 => 40pin connector => 40 knives at the back => 40 wire flat-cable UDMA/33

To allow backward compatibly the same connector and number of pins are used for all ATA-connections. However only a 40 wire flat-ribbon-cable (1,27mm between wires) is used and pressed onto the connector where 40 small knives at the back of the connector cut through the insulation to establish contact. The connector features 40 pins ( 20 pins each in in the upper and lower row)

ATA 66 => 40pin connector => 80 knives at the back => 80 wire flat-cable => ATA 66, 100, 133

The number of pins of the / physical dimensions of the connector remained identical, yet, the connector has to accommodate a 80 wire flat-ribbon-cable (0,635mm between wires). The new added 40 wires function as ground wires for which a third row of knives has been added to the connector, all of which are connected.

The additional ground wires are connected to one common ground via the center row of knives.

If you open the connector (lifting the clamp) you'll find 3 rows of knives that cut through the plastic to make the connections as shown in the picture. The connector consists of 40 pins ( 20 pins each in in the upper and lower row) and 3rows of the knives at the back for making the connection to the 80 wire flat-ribbon-cable.

Wire number 14 from the left is cut 10mm from the outermost edge of the blue connector. Wire 14 is the first address line on the cable. Cutting it here forces a high signal to show on the end device, making it the master, and allowing the cable-select pin to be used.

(thanks to Douglas Mayle for the update)

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