Reference Schematic; 40-Pin Ide Header - Emerson COM Express Carrier Design Manual

10.2 Reference Schematic

10.2.1 40-pin IDE Header

A standard 2.54 mm, two row, 40-pin connector in combination with a ribbon conductor cable is used
to interface standard 3.5 in parallel ATA drives. For slower drive speeds up to ATA33, a normal 40-pin,
1.27 mm pitch conductor cable is sufficient. Higher transfer rates such as ATA66 and ATA100 require
80-pin conductor cables, where the extra 40 conductors are tied to ground to isolate the adjacent
signals for better signal integrity. The 80-pin cable assembly also ties pin 34 (IDE_CBLID#) on the 40-
pin header to GND. If IDE_CBLID# is sampled low by the module's BIOS, it assumes that the proper
high-speed cable is present and sets up the drive parameters accordingly. Jumper settings on the IDE
devices determine master/slave configuration. The drive activity LED is driven by the module's pin A28
(COM Express pin ATA_ACT#).
Page 54 of 103 COM Express Carrier Type 2
Design Guide