Design Note; Layout Requirement; Lpt/Floppy - Advantech SOM-ETX Series Design Manual

5.9.2 Design Note

All COM Port transmitters are added on the carrier board. For designing the function
of wake on Modem you must diode-OR the RI# signal to the connector X4-D26
"RINGWAKE#".
SOM-ETX

5.9.3 Layout Requirement

Sometimes in order to avoid EMI issue, we often separate ground to frame
ground(I/O ground). Adding bead and capacitor to baseboard is necessary.
SOM-ETX
RTS#1
DTR#1
TXD1
RXD1
CTS#1
DCD#1
DSR#1
RI#1
Notes:
1. The signals TXD, DTR #, RTS# are normally outputs, but are also used as
straps during the system reset. No external pull-ups or pull downs needed
on these lines, which may affect the system configurations.
2. Pull-up resisters are needed for unused input COM ports signals(DSR#,
CTS#, RI#, DCD#). Here is an example for your reference:
Ex: use TXD and RXD only

5.10 LPT/Floppy

SOM-ETX generally supports either one parallel port or one Floppy drive. While the
parallel port is used in parallel port mode, floppy disk support is not available via the
parallel port. If both floppy drive and parallel port are needed, an external controller
may be incorporated in the baseboard design
Advantech SOM-ETX Design Guide
RTS#1
DTR#1
TXD1
Transmitter/
RXD1
CTS#1
DCD#1
DSR#1
RI#1
Figure 5-28 Serial Bus Connections
Transmitter/
Reciver
Figure 5-29 Serial Bus Layout Guidelines
Chapter 5 Carrier Board Design Guidelines
Com port
7
4
3
D-Sub 9
2
Reciver
8
1
6
9
frame ground
bead
bead
bead
bead
bead
bead
bead
bead
180p
Com port
7
4
3
D-Sub 9
2
8
1
6
9
5
93