CE-ATA connector has four data pins, and because of that is also called “4x CE-ATA” or “4-bit CE-ATA”. At first engineers tried to use the same connector used by MMC cards, but one problem emerged: crosstalk.
Crosstalk is basically when a signal carried in one wire interferes or even corrupts the signal that is being transmitted in the wire adjacent to it. Physically speaking, this happens because when we have a data being transmitted over a wire, it generates a electromagnetic field around it, and a wire inside this field acts like an antenna, capturing the signal thus modifying the signal that was being originally transmitted in that particular wire.
This is also a very particular problem on CE-ATA drives because both CF+ and MMC standards were originally created to be used by memory cards. As you know, memory cards don’t use a flat-cable to be connected to the host device (card reader): you just plug in the card inside the reader and that’s it. On CE-ATA drives, however, the engineers decided to allow them to use a small flat-cable, allowing better accommodation for the hard drive inside the consumer electronics device. However, this flat-cable helps the antenna-factor problem.
On Figure 4 you can see data being transmitted from a CE-ATA drive to a CE device using the standard MMC connector. The crosstalk was of 375 mV, which is very high.
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Figure 4: Crosstalk problem on CE-ATA using MMC connector.
The solution was to change the position of the signals on the connector. Instead of putting data signals side-by-side, engineers changed that approach and put a voltage or a ground signal between data signals, which are immune to the electromagnetic interference and work as a shield, solving the cross-talk issue.
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Figure 5: CE-ATA connector pinout compared to MMC connector pinout.
The result was a crosstalk of only 59.6 mV, as you can see on Figure 6. A crosstalk that low doesn’t interfere on the drive’s communication.
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Figure 6: Signal transmission on CE-ATA using its final connector.
