Is the pin used?
- Avoid pull conflict (2)
- Avoid logic conflict (3) if the
device is not the only driver.
- Avoid unconnected pin (1)
- Avoid pull conflicts (2)
Prefer output mode
- If possible, follow the OUTPUT guidelines
- If not possible or dynamic, follow
the INPUT guidelines
Start
Yes
Bidirectional
No
Input
Configure the pin as
an output driving 0
Pin type?
Output
Pin type?
Input
Output or Bidir
Set a pullup/down
scm-029
Public Version
www.ti.com
SCM Programming Model
Figure 13-26. I/O Power Optimization Flow Chart
The following notes give additional explanation about the pin configuration.
1. To avoid unconnected pins, the configuration depends on its use:
•
If the pin is not driven externally, a pullup/down is required.
•
Otherwise, a pullup/down is not necessary.
2. Pull conflicts occur when there are different pulls on the same line. In order to correctly configure the
pin, avoid external and internal pull together.
3. Logic conflicts consist in different electrical levels at the same time on one line. This can occur when
several devices are connected to the same line. The two possible cases are:
•
If no external device drives the line, configure the pin to drive a 0.
•
If another device drives the line, either the same value has to be driven or the pin has to be
disconnected (HZ).
NOTE:
It is advised to use high impedance logical state either on the device or the external
component when the line is driven by both components.
The I/O pads are software-controlled by:
•
Writing to the CONTROL.
registers in the control module for I/O and
pullup/down configuration.
•
Writing to the GPIOi.GPIO_OE registers in the GPIO module for I/O configuration.
For more information about how to configure the I/O pads, see
, Pad Functional Multiplexing
and Configuration.
For more information about the GPIO module, see
, General-Purpose Interface.
2543
SWPU177N – December 2009 – Revised November 2010
System Control Module
Copyright © 2009–2010, Texas Instruments Incorporated