Microchip 16F84A I/O Port B

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

Port B is a 8 bit wide bi-directional port.
Setting a bit of the TRISB register to 1 will make the corresponding bit of Port B an input.
Each Port B pin has a weak pull-up. All the weak pull-ups can be disabled by clearing bit 7 of the OPTION register (RBPU).

Maximum current sourced	100 mA
Maximum current sunk	150 mA

Port B Hardware

Pin	Name	Input	Output	Description
6	RB0	TTL	TTL	Bi-directional I/O Port
6	INT	ST	-	External Interupt
7	RB1	TTL	TTL	Bi-directional I/O Port B
8	RB2	TTL	TTL	Bi-directional I/O Port B
9	RB3	TTL	TTL	Bi-directional I/O Port B
10	RB4	TTL	TTL	Bi-directional I/O Port B, interupt-on-change pin.
11	RB5	TTL	TTL	Bi-directional I/O Port B, interupt-on-change pin.
12	RB6	TTL	TTL	Bi-directional I/O Port B, interupt-on-change pin.
13	RB7	TTL	TTL	Bi-directional I/O Port B, interupt-on-change pin.

Port B Register

Bit	Kind	Name	Description	Pwr	Other
bit 7	R/W-x	RB7	General Purpose I/O bit 1 = pin is > Vih. 0 = pin is < Vil.	x	u
bit 6	R/W-x	RB6		x	u
bit 5	R/W-x	RB5		x	u
bit 4	R/W-X	RB4		x	u
bit 3	R/W-X	RB3		x	u
bit 2	R/W-X	RB2		x	u
bit 1	R/W-X	RB1		x	u
bit 0	R/W-X	RB0		x	u

TRISB Register

Bit	Kind	Name	Description	Pwr	Other
bit 7	R/W-1	TRISB7	1 = pin is configured as an input. 0 = pin is configured as an output.	1	1
bit 6	R/W-1	TRISB6		1	1
bit 5	R/W-1	TRISB5		1	1
bit 4	R/W-1	TRISB4		1	1
bit 3	R/W-1	TRISB3		1	1
bit 2	R/W-1	TRISB2		1	1
bit 1	R/W-1	TRISB1		1	1
bit 0	R/W-1	TRISB0		1	1

        BCF     STATUS, RP0     ;
        CLRF    PORTB           ; Initialize PORTB by
                                ; clearing output
                                ; data latches
        BSF     STATUS, RP0     ; Select Bank 1
        MOVLW   b'11001111'     ; Value used to
                                ; initialize data
                                ; direction
        MOVWF   TRISB           ; Set RB7-RB6 and RB3-RB0 as inputs
                                ; RB5-RB4 as outputs