DSPIC33EP64GS708 datasheet(132/484 Pages) MICROCHIP

132 / 484 page

dsPIC33EPXXXGS70X/80X FAMILY

DS70005258C-page 132

 2016-2018 Microchip Technology Inc.

11.2.1

OPEN-DRAIN CONFIGURATION

In addition to the PORTx, LATx and TRISx registers

for data control, port pins can also be individually

configured for either digital or open-drain output. This

is controlled by the Open-Drain Control x 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 out-

puts other than VDD by using external pull-up resistors.

The maximum open-drain voltage allowed on any pin

is the same as the maximum VIH specification for that

particular pin. See the “Pin Diagrams” section for the

available 5V tolerant pins and Table 30-11 for the

maximum VIH specification for each pin.

11.3

Configuring Analog and Digital

Port Pins

The ANSELx register controls the operation of the

analog port pins. The port pins that are to function as

analog inputs or outputs must have their corresponding

ANSELx and TRISx bits set. In order to use port pins for

I/O functionality with digital modules, such as timers,

UARTs, etc., the corresponding ANSELx bit must be

cleared.

The ANSELx register has a default value of 0xFFFF;

therefore, all pins that share analog functions are

analog (not digital) by default.

Pins with analog functions affected by the ANSELx

registers are listed with a buffer type of analog in the

Pinout I/O Descriptions (see Table 1-1). Table 11-1

through Table 11-5 show ANSELx bits’ availability for

device variants.

If the TRISx bit is cleared (output) while the ANSELx bit

is set, the digital output level (VOH or VOL) is converted

by an analog peripheral, such as the ADC module or

comparator module.

When the PORTx register is read, all pins configured as

analog input channels are read as cleared (a low level).

Pins configured as digital inputs do not convert an

analog input. Analog levels on any pin, defined as a

digital input (including the ANx pins), can cause the

input buffer to consume current that exceeds the

device specifications.

11.3.1

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, as shown in Example 11-1.

11.4

Input Change Notification (ICN)

The Input Change Notification function of the I/O ports

allows devices to generate interrupt requests to the

processor in response to a Change-of-State (COS) on

selected input pins. This feature can detect input

Change-of-States, even in Sleep mode, when the

clocks are disabled. Every I/O port pin can be selected

(enabled) for generating an interrupt request on a

Change-of-State.

Three control registers are associated with the ICN

functionality of each I/O port. The CNENx registers

contain the ICN interrupt enable control bits for each of

the input pins. Setting any of these bits enables an ICN

interrupt for the corresponding pins.

Each I/O pin also has a weak pull-up and a weak

pull-down connected to it. The pull-ups and pull-

downs act as a current source, or sink source,

connected to the pin, and eliminate the need for

external resistors when push button or keypad

devices are connected. The pull-ups and pull-downs

are enabled separately, using the CNPUx and the

CNPDx registers, which contain the control bits for

each of the pins. Setting any of the control bits

enables the weak pull-ups and/or pull-downs for the

corresponding pins.

EXAMPLE 11-1:

PORT WRITE/READ

EXAMPLE

Note:

Pull-ups and pull-downs on Input Change

Notification pins

should always be

disabled when the port pin is configured

as a digital output.

MOV

0xFF00, W0

; Configure PORTB<15:8>

; as inputs

MOV

W0, TRISB

; and PORTB<7:0>

; as outputs

NOP

; Delay 1 cycle

BTSS

PORTB, #13

; Next Instruction

DSPIC33EP64GS708 数据表(PDF) 132 Page - Microchip Technology

DSPIC33EP64GS708 数据表(HTML) 132 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载