PIC24FJ128GC010 Datasheet, PDF (38/472 Pages) Microchip Technology – 16-Bit Flash Microcontrollers with 12-Bit Pipeline A/D, Sigma-Delta A/D, USB On-The-Go and XLP Technology

PIC24FJ128GC010 FAMILY
2.7 Configuration of Analog and
Digital Pins During ICSP
Operations
If an ICSP compliant emulator is selected as a debug-
ger, it automatically initializes all of the A/D input pins
(ANx) as “digital” pins. Depending on the particular
device, this is done by setting all bits in the ADnPCFG
register(s), or clearing all bit in the ANSx registers.
All PIC24F devices will have either one or more
ADnPCFG registers or several ANSx registers (one for
each port); no device will have both. Refer to
Section 11.2 “Configuring Analog Port Pins
(ANSx)” for more specific information.
The bits in these registers that correspond to the A/D
pins that initialized the emulator must not be changed
by the user application firmware; otherwise,
communication errors will result between the debugger
and the device.
If your application needs to use certain A/D pins as
analog input pins during the debug session, the user
application must modify the appropriate bits during
initialization of the A/D module, as follows:
• For devices with an ADnPCFG register, clear the
bits corresponding to the pin(s) to be configured
as analog. Do not change any other bits, particu-
larly those corresponding to the PGECx/PGEDx
pair, at any time.
• For devices with ANSx registers, set the bits
corresponding to the pin(s) to be configured as
analog. Do not change any other bits, particularly
those corresponding to the PGECx/PGEDx pair,
at any time.
When a Microchip debugger/emulator is used as a
programmer, the user application firmware must
correctly configure the ADnPCFG or ANSx registers.
Automatic initialization of this register is only done
during debugger operation. Failure to correctly
configure the register(s) will result in all A/D pins being
recognized as analog input pins, resulting in the port
value being read as a logic ‘0’, which may affect user
application functionality.
2.8 Sigma-Delta A/D Connections
The Sigma-Delta A/D Converter has input and power
connections that are independent from the rest of the
microcontroller. These connections are required to use
the converter, and are in addition to the connection and
layout connections provided in Section 2.1 “Basic
Connection Requirements” and Section 2.2 “Power
Supply Pins”.
2.8.1
VOLTAGE AND GROUND
CONNECTIONS
To minimize noise interference, the Sigma-Delta A/D
Converter has independent voltage pins. Converter cir-
cuits are supplied through the SVDD pin. Independent
ground return is provided through the SVss pin.
As with the microcontroller’s VDD/VSS and AVDD/AVSS
pins, bypass capacitors are required on SVDD and SVSS.
Requirements for these capacitors are identical to those
for the VDD/VSS and AVDD/AVSS pins.
It is recommended that designs using the Sigma-Delta
A/D Converter incorporate a separate ground return
path for analog circuits. The analog and digital grounds
may be tied to a single point at the power source. Ana-
log pins that require grounding should be tied to this
analog return. SVSS can be tied to the digital ground,
along with VSS and AVSS.
2.8.2 ANALOG INPUTS
The analog signals to be converted are connected to the
pins of CH0 and/or CH1. Each channel has inverting and
non-inverting inputs (CHn- and CHn+, respectively), and
is fully differential.
If not used for conversion, CH1+ and CH1- can be used
to supply an external voltage reference to the con-
verter. If an external reference is not used and CH1 is
not needed as a conversion input, both pins should be
connected to the analog ground return.
2.9 Unused I/Os
Unused I/O pins should be configured as outputs and
driven to a logic low state. Alternatively, connect a 1 kΩ
to 10 kΩ resistor to VSS on unused pins and drive the
output to logic low.
DS30009312B-page 38
 2012-2013 Microchip Technology Inc.