PIC16C765 Microchip Technology Inc., PIC16C765 Datasheet - Page 31

• Manufacturer Part Number: PIC16C765
• Description: 8-bit Cmos Microcontrollers With Usb
• Manufacturer: Microchip Technology Inc.

5.0
Some pins for these I/O ports are multiplexed with an
alternate function 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 is a 6-bit latch.
The RA4/T0CKI pin is a Schmitt Trigger input and an
open drain output. All other RA port pins have TTL
input levels and full CMOS output drivers. All pins have
data direction bits (TRIS registers), which can config-
ure these pins as output or input.
Setting a TRISA register bit puts the corresponding out-
put driver in a hi-impedance mode. Clearing a bit in the
TRISA register puts the contents of the output latch on
the selected pin(s).
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, the value is modified, and then written to the port
data latch.
Pin RA4 is multiplexed with the Timer0 module clock
input to become the RA4/T0CKI pin.
On the PIC16C745/765, PORTA pins are multiplexed
with analog inputs and analog V
tion of each pin is selected by clearing/setting the con-
trol bits in the ADCON1 register (A/D Control
Register1).
The TRISA register controls the direction of the RA
pins, even when they are being used as analog inputs.
The user must ensure the bits in the TRISA register are
maintained set when using them as analog inputs.
EXAMPLE 5-1:
BCF
BCF
CLRF
BSF
MOVLW
MOVWF
MOVLW
MOVWF
2000 Microchip Technology Inc.
Note:
I/O PORTS
PORTA and TRISA Registers
STATUS, RP1
STATUS, RP0
PORTA
STATUS, RP0
0x06
ADCON1
0xCF
TRISA
On all RESETS, pins with analog and digi-
tal functions are configured as analog
inputs.
INITIALIZING PORTA
(PIC16C745/765)
;
;
; Initialize PORTA by
; clearing output
; data latches
; Select Bank 1
; Configure all pins
; as digital inputs
; Value used to
; initialize data
; direction
; Set RA<3:0> as inputs
; RA<5:4> as outputs
; TRISA<7:6> are always
; read as ’0’.
REF
input. The opera-
Preliminary
FIGURE 5-1:
FIGURE 5-2:
Data
Bus
WR
Port
WR
TRIS
RD Port
To A/D Converter
WR
TRIS
Data
Bus
WR
Port
RD Port
TMR0 Clock Input
D
D
TRIS Latch
Data Latch
CK
CK
TRIS Latch
Data Latch
PIC16C745/765
D
D
CK
CK
BLOCK DIAGRAM OF RA<3:0>
AND RA5 PINS
BLOCK DIAGRAM OF
RA4/T0CKI PIN
RD TRIS
Q
Q
Q
Q
RD TRIS
Q
Q
Q
Q
Q
Q
Schmitt
Trigger
Input
Buffer
EN
Schmitt Trigger
Input Buffer
EN
EN
D
D
Analog
Input
Mode
V
DS41124C-page 31
N
SS
V
V
P
N
SS
DD
V
DD
V
DD
I/O pin
I/O Pin