Microchip 16F84A I/O Port A

Programming | PIC's | 16F84A | I/O Port A

Port A is a 5 bit wide bi-directional port.
Setting a bit of the TRISA register to 1 will make the corresponding bit of Port A an input.

Maximum current sourced	50 mA
Maximum current sunk	80 mA

Port B Hardware

Pin	Name	Input	Output	Description
17	RA0	TTL	TTL	Bi-directional I/O Port A
18	RA1	TTL	TTL	Bi-directional I/O Port A
1	RA2	TTL	TTL	Bi-directional I/O Port A
2	RA3	TTL	TTL	Bi-directional I/O Port A
3	RA4	TTL	TTL	Bi-directional I/O Port A
3	T0CKI	ST	OD	clock input to the TMR0 timer/counter.

Port A Register

Bit	Kind	Name	Description	Pwr	Other
bit 7	U-0		Unimplemented bit	-	-
bit 6	U-0		Unimplemented bit	-	-
bit 5	U-0		Unimplemented bit	-	-
bit 4	R/W-X	RA4	General Purpose I/O bit 1 = pin is > Vih. 0 = pin is < Vil.	x	u
bit 3	R/W-X	RA3		x	u
bit 2	R/W-X	RA2		x	u
bit 1	R/W-X	RA1		x	u
bit 0	R/W-X	RA0		x	u

TRISA Register

Bit	Kind	Name	Description	Pwr	Other
bit 7	U-0		Unimplemented bit	-	-
bit 6	U-0		Unimplemented bit	-	-
bit 5	U-0		Unimplemented bit	-	-
bit 4	R/W-1	TRISA4	1 = pin is configured as an input. 0 = pin is configured as an output.	1	1
bit 3	R-1	TRISA3		1	1
bit 2	R/W-1	TRISA2		1	1
bit 1	R/W-1	TRISA1		1	1
bit 0	R/W-1	TRISA0		1	1

Sample code to initialize PORT A

        BCF     STATUS, RP0         ; select bank 0
        CLRF    PORTA               ; Initialize PORTA by
                                    ; clearing output
                                    ; data latches
        BSF     STATUS, RP0         ; Select Bank 1
        MOVLW   0x0F                ; Value used to
                                    ; initialize data
                                    ; direction
        MOVWF   TRISA               ; Set RA3 through RA0 as inputs, RA4 as output
                                    ; TRISA bits 7 through 5 are always read as 0.