70592C Datasheet, PDF (26/314 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJXXXGPX06A/X08A/X10A
2.7 Oscillator Value Conditions on
Device Start-up
If the PLL of the target device is enabled and
configured for the device start-up oscillator, the
maximum oscillator source frequency must be limited
to ≤8 MHz for start-up with PLL enabled to comply with
device PLL start-up conditions. This means that if the
external oscillator frequency is outside this range, the
application must start-up in the FRC mode first. The
default PLL settings after a POR with an oscillator
frequency outside this range will violate the device
operating speed.
Once the device powers up, the application firmware
can initialize the PLL SFRs, CLKDIV and PLLDBF to a
suitable value, and then perform a clock switch to the
Oscillator + PLL clock source. Note that clock switching
must be enabled in the device Configuration word.
2.8 Configuration of Analog and
Digital Pins During ICSP
Operations
If MPLAB ICD 2, ICD 3 or REAL ICE is selected as a
debugger, it automatically initializes all of the A/D input
pins (ANx) as “digital” pins, by setting all bits in the
AD1PCFGL register.
The bits in this register that correspond to the A/D pins
that are initialized by MPLAB ICD 2, ICD 3, or REAL
ICE, must not be cleared 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 clear the corresponding bits in the
AD1PCFGL register during initialization of the ADC
module.
When MPLAB ICD 2, ICD 3 or REAL ICE is used as a
programmer, the user application firmware must
correctly configure the AD1PCFGL register. 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.
2.9 Unused I/Os
Unused I/O pins should be configured as outputs and
driven to a logic-low state.
Alternatively, connect a 1k to 10k resistor between VSS
and the unused pins.
DS70592C-page 26
© 2011 Microchip Technology Inc.