PIC16C641-04ESLASHTQ datasheet(29/136 Pages) MICROCHIP

29 / 136 page

Preliminary

DS30559A-page 29

PIC16C64X & PIC16C66X

5.0

I/O PORTS

The PIC16C641 and PIC16C642 have three ports,

PORTA,

PORTB,

and

PORTC.

PIC16C661

and

PIC16C662 devices have ﬁve ports, PORTA through

PORTE. Some pins for these I/O ports are multiplexed

with alternate functions for the peripheral features on

the device. In general, when a peripheral is enabled,

that pin may not be used as a general purpose I/O pin.

5.1

PORTA and TRISA Registers

PORTA is a 6-bit wide latch. RA4 is a Schmitt Trigger

input and an open drain output. Pin RA4 is multiplexed

with the T0CKI clock input. All other RA port pins have

Schmitt Trigger input levels and full CMOS output driv-

ers. All pins have data direction bits (TRIS registers)

which can conﬁgure these pins as input or output.

Setting a bit in the TRISA register puts the correspond-

ing output driver in a hi-impedance mode. Clearing a bit

in the TRISA register puts the contents of the output

latch on the selected pin.

Reading the PORTA register reads the status of the

pins, whereas writing to it will write to the port latch. All

write operations are read-modify-write operations.

Therefore, a write to a port implies that the port pins are

read, this value is modiﬁed, and then written to the port

data latch.

The PORTA pins are multiplexed with comparator and

voltage reference functions. The operation of these

pins are selected by control bits in the CMCON

(comparator control register) register and the VRCON

(voltage reference control) register. When selected as

comparator inputs, these pins will read as '0's.

FIGURE 5-1:

BLOCK DIAGRAM OF

RA1:RA0 PINS

TRISA controls the direction of the RA pins, even when

they are being used as comparator inputs. The user

must make sure to keep the pins conﬁgured as inputs

when using them as comparator inputs.

The RA2 pin will also function as the output for the

voltage reference. When in this mode, the VREF pin is

a very hi-impedance output. The user must set the

TRISA<2> bit and use hi-impedance loads.

In one of the comparator modes deﬁned by the

CMCON register, pins RA3 and RA4 become outputs

of the comparators. The TRISA<4:3> bits must be

cleared to enable outputs to use this function.

EXAMPLE 5-1:

INITIALIZING PORTA

CLRF

PORTA

;Initialize PORTA by

;clearing output latches

MOVLW

0x07

;Turn comparators off,

MOVWF

CMCON

;enable pins for I/O

BSF

STATUS, RP0

;Select bank1

MOVLW

0x1F

;Value to initialize

;data direction

MOVWF

TRISA

;Set RA<4:0> as inputs

;TRISA<7:5> are clear

Note:

On reset, the TRISA register is set to all

inputs. The digital inputs are disabled and

the comparator inputs are forced to ground

to reduce excess current consumption.

Note: I/O pins have protection diodes to VDD and VSS.

Data

bus

Port

TRIS

Data Latch

TRIS Latch

RD TRIS

RD PORT

Analog

VSS

VDD

I/O Pin

Input Mode

To Comparator

Schmitt Trigger

Input Buffer

This document was created with FrameMaker404

PIC16C641-04E/TQ Datasheet(PDF) 29 Page - Microchip Technology

PIC16C641-04E/TQ Datasheet(HTML) 29 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

Datasheet Download

Link URL