PIC16C774 Microchip Technology Inc., PIC16C774 Datasheet - Page 29

• Manufacturer Part Number: PIC16C774
• Description: 28/40-pin, 8-bit Cmos Microcontrollers W/ 12-bit A/d
• Manufacturer: Microchip Technology Inc.

3.2
PORTB is an 8-bit wide bi-directional port. The corre-
sponding data direction register is TRISB. Setting a
TRISB bit (=1) will make the corresponding PORTB pin
an input, i.e., put the corresponding output driver in a
hi-impedance mode. Clearing a TRISB bit (=0) will
make the corresponding PORTB pin an output, i.e., put
the contents of the output latch on the selected pin.
EXAMPLE 3-1:
BCF
CLRF
BSF
MOVLW
MOVWF
Each of the PORTB pins has a weak internal pull-up. A
single control bit can turn on all the pull-ups. This is per-
formed by clearing bit RBPU (OPTION_REG<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are dis-
abled on a Power-on Reset.
The RB0 pin is multiplexed with the external interrupt
(RB0/INT).
FIGURE 3-4:
Data bus
WR TRIS
WR Port
RBPU
RB0/INT
1999 Microchip Technology Inc.
Note 1: I/O pins have diode protection to V
(2)
2: To enable weak pull-ups, set the appropriate TRIS bit(s)
STATUS, RP0
PORTB
STATUS, RP0
0xCF
TRISB
PORTB and the TRISB Register
and clear the RBPU bit (OPTION_REG<7>).
BLOCK DIAGRAM OF RB0 PIN
RD TRIS
RD Port
TRIS Latch
Data Latch
INITIALIZING PORTB
D
D
CK
CK
Schmitt Trigger
Buffer
;
; Initialize PORTB by
; clearing output
; data latches
; Select Bank 1
; Value used to
; initialize data
; direction
; Set RB<3:0> as inputs
; RB<5:4> as outputs
; RB<7:6> as inputs
Q
Q
Q
DD
and V
EN
TTL
Input
Buffer
D
SS
Advance Information
.
V
P
RD Port
DD
weak
pull-up
I/O
pin
(1)
The RB1 pin is multiplexed with the SSP module slave
select (RB1/SS).
FIGURE 3-5:
The RB2 pin is multiplexed with analog channel 8
(RB2/AN8).
FIGURE 3-6:
Data bus
Data bus
WR TRIS
WR TRIS
WR Port
WR Port
SS input
To A/D converter
RBPU
RBPU
Note 1: I/O pins have diode protection to V
Note 1: I/O pins have diode protection to V
(2)
(2)
2: To enable weak pull-ups, set the appropriate TRIS bit(s)
2: To enable weak pull-ups, set the appropriate TRIS bit(s)
and clear the RBPU bit (OPTION_REG<7>).
and clear the RBPU bit (OPTION_REG<7>).
RD TRIS
Data Latch
TRIS Latch
D
D
CK
CK
BLOCK DIAGRAM OF RB1/SS
BLOCK DIAGRAM OF
PIN
RB2/AN8 PIN
RD TRIS
RD Port
RD Port
Data Latch
TRIS Latch
D
D
Q
Q
CK
CK
Schmitt Trigger
Buffer
PIC16C77X
Q
Q
Q
Analog
input mode
EN
D
Q
DD
DD
DS30275A-page 29
and V
and V
EN
TTL
Input
Buffer
TTL
Input
Buffer
RD Port
D
SS
SS
.
.
V
V
P
RD Port
P
DD
DD
weak
pull-up
weak
pull-up
I/O
pin
I/O
pin
(1)
(1)