PIC24HJ12GP201 Datasheet, PDF (92/234 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJ12GP201/202
9.1.1 OPEN-DRAIN CONFIGURATION
In addition to the PORT, LAT and TRIS registers for
data control, each port pin can also be individually
configured for either digital or open-drain output. This
is controlled by the Open-Drain Control register,
ODCx, associated with each port. Setting any of the
bits configures the corresponding pin to act as an
open-drain output.
The open-drain feature allows the generation of
outputs higher than VDD (e.g., 5V) on any desired
digital-only pins by using external pull-up resistors.
The maximum open-drain voltage allowed is the same
as the maximum VIH specification.
9.2 Configuring Analog Port Pins
The AD1PCFG and TRIS registers control the opera-
tion of the Analog-to-Digital (A/D) port pins. The port
pins that are desired as analog inputs must have their
corresponding TRIS bit set (input). If the TRIS bit is
cleared (output), the digital output level (VOH or VOL)
will be converted.
When the PORT register is read, all pins configured as
analog input channels will read as cleared (a low level).
Pins configured as digital inputs will not convert an
analog input. Analog levels on any pin that is defined as
a digital input (including the ANx pins) can cause the
input buffer to consume current that exceeds the
device specifications.
9.2.1 I/O PORT WRITE/READ TIMING
One instruction cycle is required between a port
direction change or port write operation and a read
operation of the same port. Typically this instruction
would be a NOP. An example is shown in Example 9-1.
9.3 Input Change Notification
The input change notification function of the I/O ports
allows the PIC24HJ12GP201/202 devices to generate
interrupt requests to the processor in response to a
change-of-state on selected input pins. This feature
can detect input change-of-states even in Sleep mode,
when the clocks are disabled. Depending on the device
pin count, up to 21 external signals (CNx pin) can be
selected (enabled) for generating an interrupt request
on a change-of-state.
Four control registers are associated with the CN
module. The CNEN1 and CNEN2 registers contain the
interrupt enable control bits for each of the CN input
pins. Setting any of these bits enables a CN interrupt
for the corresponding pins.
Each CN pin also has a weak pull-up connected to it.
The pull-ups act as a current source connected to the
pin, and eliminate the need for external resistors when
push button or keypad devices are connected. The
pull-ups are enabled separately using the CNPU1 and
CNPU2 registers, which contain the control bits for
each of the CN pins. Setting any of the control bits
enables the weak pull-ups for the corresponding pins.
Note:
Pull-ups on change notification pins
should always be disabled when the port
pin is configured as a digital output.
EXAMPLE 9-1: PORT WRITE/READ EXAMPLE
MOV
MOV
NOP
btss
0xFF00, W0
W0, TRISBB
PORTB, #13
; Configure PORTB<15:8> as inputs
; and PORTB<7:0> as outputs
; Delay 1 cycle
; Next Instruction
DS70282B-page 90
Preliminary
© 2007 Microchip Technology Inc.