Microchip Technology dsPIC30F - Port Descriptions; Change Notification (CN) Pins

© 2004 Microchip Technology Inc. DS70058C-page 11-5
Section 11. I/O Ports
I/O Ports
11
11.3.1.1 Software Input Pin Control
Some of the functions assigned to an I/O pin may be input functions that do not take control of
the pin output driver. An example of one such peripheral is the Input Capture module. If the I/O
pin associated with the Input Capture is configured as an output, using the appropriate
TRIS control bit, the user can manually affect the state of the Input Capture pin through its
corresponding PORT register. This behavior can be useful in some situations, especially for
testing purposes, when no external signal is connected to the input pin.
Referring to Figure 11-2, the organization of the peripheral multiplexers will determine if the peripheral
input pin can be manipulated in software using the PORT register. The conceptual peripherals shown
in this figure disconnect the PORT data from the I/O pin when the peripheral function is enabled.
In general, the following peripherals allow their input pins to be controlled manually through the
PORT registers:
• External Interrupt pins
• Timer Clock Input pins
• Input Capture pins
• PWM Fault pins
Most serial communication peripherals, when enabled, take full control of the I/O pin, so that the
input pins associated with the peripheral cannot be affected through the corresponding PORT
registers. These peripherals include the following:
•SPI
TM
•I
2
C
TM
• DCI
•UART
•CAN
11.4 Port Descriptions
Refer to the device data sheet for a description of the available I/O ports and peripheral
multiplexing details.
11.5 Change Notification (CN) Pins
The Change Notification (CN) pins provide dsPIC30F devices the ability to generate interrupt
requests to the processor in response to a change of state on selected input pins. Up to 24 input pins
may be selected (enabled) for generating CN interrupts. The total number of available CN inputs is
dependent on the selected dsPIC30F device. Refer to the device data sheet for further details.
Figure 11-3 shows the basic function of the CN hardware.
Figure 11-3: Input Change Notification Block Diagram
CN
DQ
C
DQ
C
CN0IE (CNEN1<0>)
CN0
pin
CN0PUE
(CNPU1<0>)
CN0 Change
CN1 Change
CN23 Change
Interrupt
CN1-CN23
Details Not
Shown