PIC24FJ64GA705 Datasheet, PDF (126/412 Pages) –

PIC24FJ256GA705 FAMILY
11.1.1 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.
11.1.2 OPEN-DRAIN CONFIGURATION
In addition to the PORTx, LATx and TRISx registers for
data control, each port pin can also be individually
configured for either a digital or open-drain output. This
is controlled by the Open-Drain Control register, ODCx,
associated with each port. Setting any of the bits con-
figures 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.
11.2 Configuring Analog Port Pins (ANSx)
The ANSx and TRISx registers control the operation of
the pins with analog function. Each port pin with analog
function is associated with one of the ANSx bits, which
decide if the pin function should be analog or digital.
Refer to Table 11-1 for detailed behavior of the pin for
different ANSx and TRISx bit settings.
When reading the PORTx register, all pins configured as
analog input channels will read as cleared (a low level).
11.2.1
ANALOG INPUT PINS AND
VOLTAGE CONSIDERATIONS
The voltage tolerance of pins used as device inputs is
dependent on the pin’s input function. Most input pins
are able to handle DC voltages of up to 5.5V, a level typ-
ical for digital logic circuits. However, several pins can
only tolerate voltages up to VDD. Voltage excursions
beyond VDD on these pins should always be avoided.
Table 11-2 summarizes the different voltage toler-
ances. For more information, refer to Section 32.0
“Electrical Characteristics” for more details.
TABLE 11-1: CONFIGURING ANALOG/DIGITAL FUNCTION OF AN I/O PIN
Pin Function
ANSx Setting
TRISx Setting
Comments
Analog Input
1
Analog Output
1
Digital Input
0
Digital Output
0
1
It is recommended to keep ANSx = 1.
1
It is recommended to keep ANSx = 1.
1
Firmware must wait at least one instruction cycle
after configuring a pin as a digital input before a valid
input value can be read.
0
Make sure to disable the analog output function on
the pin if any is present.
TABLE 11-2: INPUT VOLTAGE LEVELS FOR PORT OR PIN TOLERATED DESCRIPTION INPUT
Port or Pin
Tolerated Input
Description
PORTB<11:10,8:5>
PORTC<9:6>
PORTA<14:7,4:0>
PORTB<15:12,9,4:0>
PORTC<5:0>
5.5V
VDD
Tolerates input levels above VDD; useful
for most standard logic.
Only VDD input levels are tolerated.
DS30010118B-page 126
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