User manual

Advantech SOM-Express Design Guide
Chapter 5 Carrier Board Design Guidelines 63
Figure 5-26 IDE0 Connections
5.6.2.4 CompactFlash Socket Implementation Notes
The CompactFlash (CF) card cannot be hot-plugged (changed while the system is
powered). If hot-plug support is necessary, then a PCI-based CardBus controller chip
can be integrated onto the carrier board and used to control the CF socket. The CF
card can be configured as a slave device when the CSEL signal is set as non-
connection. If two CF cards (or a CF card and a hard drive) are used in the
master/slave mode on the same IDE port, the IDE_CBLID# pins on both devices
must be connected. These pins negotiate between the master and slave devices.
The devices may not function correctly unless these pins are interconnected.
5.6.3 Layout Guidelines
5.6.3.1 IDE data and strobe routing guideline
This section contains guidelines for connecting and routing the IDE interface. SOM-
Express provides one independent IDE channel. This section provides guidelines for
IDE connector cabling and carrier board design. Additional external 0 # resistors can
be incorporated into the design to address possible noise issues on the carrier board.
If used, these resistors should be placed close to the connector.
The IDE interface can be routed with 6-mil traces on 6-mil spaces (dependent upon
stack-up parameters), and must be less than 10 inches long (from SOM-Express
connector to carrier board IDE connector). Additionally, the maximum length
difference between the data signals and the strobe signal of a channel is 450 mils.
Table 5-18 IDE Routing Summary
Trace Impedance
IDE Routing
requirements
Trace length IDE Signal length matching
55 # ± 15%
6 on 6 (Based
on stack-up in
chap 4)
1 ~ 10 inches
The two strobe signals must be
matched within 100 mils of each other.
The data lines must be within ± 450
mils of the average length of the two
strobe signals
SOM
-
ETX
IDE
_
IOW#
IDE
_
IOR #
IDE
_
A
CK #
IDE
_
CS # 1
IDE
_
CS # 3
IDE
_
A
[ 0 : 2 ]
IDE
_
D[0 : 15 ]
IDE
_
IRQ
IDE
_
IORDY
IDE
_
REQ
IDE
_
CBLID
IDE
Connecto
r