PIC16F15213 datasheet(127/439 Pages) MICROCHIP

127 / 439 page

Reading the PORTx 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, and

this value is modified, then written to the PORT data latch (LATx). The PORT data latch LATx holds the output port

data and contains the latest value of a LATx or PORTx write. The example below shows how to initialize PORTA.

Example 16-1. Initializing PORTA in Assembly

; This code example illustrates initializing the PORTA register.

; The other ports are initialized in the same manner.

BANKSEL

PORTA

;

CLRF

PORTA

;Clear PORTA

BANKSEL

LATA

;

CLRF

LATA

;Clear Data Latch

BANKSEL

ANSELA

;

CLRF

ANSELA

;Enable digital drivers

BANKSEL

TRISA

;

MOVLW

B'00111000'

;Set RA[5:3] as inputs

MOVWF

TRISA

;and set others as outputs

Example 16-2. Initializing PORTA in C

// This code example illustrates initializing the PORTA register.

// The other ports are initialized in the same manner.

PORTA

= 0x00;

// Clear PORTA

LATA

= 0x00;

// Clear Data Latch

ANSELA = 0x00;

// Enable digital drivers

TRISA

= 0x38;

// Set RA[5:3] as inputs and set others as outputs

Important: Most PORT pins share functions with device peripherals, both analog and digital. In general,

when a peripheral is enabled on a PORT pin, that pin cannot be used as a general purpose output;

however, the pin can still be read.

16.3

LATx - Output Latch

The Data Latch (LATx registers) is useful for Read-Modify-Write operations on the value that the I/O pins are driving.

A write operation to the LATx register has the same effect as a write to the corresponding PORTx register. A read

of the LATx register reads of the values held in the I/O PORT latches, while a read of the PORTx register reads the

actual I/O pin value.

Important: As a general rule, output operations to a port must use the LAT register to avoid Read-

Modify-Write issues. For example, a bit set or clear operation reads the port, modifies the bit, and writes

the result back to the port. When two bit operations are executed in succession, output loading on the

changed bit may delay the change at the output in which case the bit will be misread in the second bit

operation and written to an unexpected level. The LAT registers are isolated from the port loading and

therefore changes are not delayed.

PIC16F15213/14/23/24/43/44

I/O Ports

and its subsidiaries

Data Sheet

DS40002195E-page 127

PIC16F15213 Datasheet(PDF) 127 Page - Microchip Technology

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