CME136686LX Hardware Manual - RTD Embedded Technologies ...
CME136686LX Hardware Manual - RTD Embedded Technologies ...
CME136686LX Hardware Manual - RTD Embedded Technologies ...
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IDE Controller Configuration<br />
The CPU’s onboard EIDE connector (CN10) supports several different drive speed modes, which are BIOS<br />
configurable. Supported drive modes will depend on whether a 40-conductor or 80-conductor cable is<br />
connecting the EIDE device. The modes and cable detection schemes described below may be set in the BIOS<br />
Setup. Similarly, the ATA/IDE Disk Chip socket (U16) is BIOS configurable.<br />
Cable Modes<br />
There are two types of cables that may be used for connecting drives to the EIDE connector: 40 conductor cables<br />
or 80 conductor cables. Depending on the cable used, different drive speeds are supported. A 40 conductor cable<br />
can be used for speeds up to UDMA Mode 2 (Ultra ATA/33).<br />
In order to use drive speeds faster than UDMA Mode 2 (Ultra ATA/33), an 80 conductor cable is required. The<br />
BIOS can be configured to detect the presence of an 80 conducto7r cable. The 80 conductor cable adds a ground<br />
wire between each signal, and uses standard 40 pin connectors.<br />
Note An 80-conductor cable should not be used if an ATA/IDE Disk Chip is installed in the cpuModule.<br />
For more information, refer to the section titled: Using the ATA/IDE Disk Chip and EIDE<br />
Cable Detection<br />
Every time the cpuModule is powered on or a hardware reset is issued, the BIOS will automatically detect the<br />
presence of a 80 conductor cable connecting a device to CN10. The user selectable cable detection modes are<br />
described below.<br />
Device and Host Mode<br />
For this method, there is a capacitor on the CBLID pin at the CPU, and a pull-up at the hard drive. The CPU sends<br />
a command to the hard drive to drive the CBLID pin low, and then release it. The CPU then waits a certain<br />
amount of time, and instructs the hard drive to read the status of the CBLID pin. If an 80 conductor cable is<br />
attached, the CBLID signal is not connected between the CPU and the hard drive, and the hard drive will read<br />
the signal as a logic high. If a 40 conductor cable is attached, the CBLID pin is connected between the CPU and<br />
the hard drive, the capacitor delays the signal from going high, and the hard drive reads it as a logic low.<br />
Host Determination of Cable Type<br />
For this method of detection, the CPU reads the CPBLID pin, which determines if a 40-conductor or 80-<br />
conductor cable is connected between the CPU and device. An 80-conductor cable has this signal grounded at<br />
the CPU end, and not connected to the hard drive. A 40-conductor cable connects the CBLID signal to the hard<br />
drive, where it is pulled to a logic high.<br />
Device Detect<br />
For device detect mode, the CPU issues a command to the device, which tells the CPU the fastest drive speed<br />
mode it can use. The CPU then sets the transfer mode to the fastest speed supported by the device.<br />
WARNING When this cable detection method is enabled, the highest transfer speed supported by the<br />
device will be used regardless of whether a 40-conductor or 80-conductor cable is used. If the device speed<br />
does not match the cable, data corruption and unexpected behaviors may occur. This mode should not<br />
be selected unless the user knows the cable type and the modes supported by the connected EIDE device.<br />
72 <strong>CME136686LX</strong> cpuModule BDM-610000065 Rev C