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.
In 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.
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.
The result was a crosstalk of only 59.6 mV, as you can see in Figure 6. A crosstalk that low doesn’t interfere on the drive’s communication.