Carrier Board Design Guide for SOM-9X35 Module
3
1.3
I/O Parameter Definitions
Symbol
Description
Pad attribute
AI
Analog Input (does not include the pad circuitry)
AO
Analog Output (does not include the pad circuitry)
B
Bidirectional digital with CMOS input
DI
Digital Input (CMOS)
DO
Digital Output (CMOS)
H
High-Voltage tolerant
S
Schmitt trigger input
Z
High-impedance (high-Z) output
Pad pull details for digital I/O
nppdpukp
Programmable pull resistor. The default pull direction is indicated using capital
letters and is a prefix to other programmable options:
NP:pdpukp = default no-pull with programmable options following the colon (:)
PD:nppukp = default pull-low (pull-down) with programmable options following
the colon (:)
PU:nppdkp = default pull-high (pull-up) with programmable options following the
colon (:)
KP:nppdpu = default keeper with programmable options following the colon (:)
KP
Contains an internal weak keeper device (keepers cannot drive external buses)
NP
Contains no internal pull
PU
Contains an internal pull-high device
PD
Contains an internal pull-low device
Table 02: I/O parameter definitions
1.4
Schematic Conventions
The reference schematics depicted in this document show the directional flows of the signals. Directional flow
is indicated by the pointed ends of the arrow shapes.
Bidirec�onal signal flow
IC/Connector
Input signal flow
Output signal flow
Figure 01: Schematic conventions
