PIC16C923-04I/CL Microchip Technology, PIC16C923-04I/CL Datasheet - Page 31

• Manufacturer Part Number: PIC16C923-04I/CL
• Description: 8-Bit CMOS Microcontroller with LCD Driver
• Manufacturer: Microchip Technology

5.0
Some pins for these ports are multiplexed with an alter-
nate 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
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 RA pins have
data direction bits (TRISA register) which can configure
these pins as output or input.
Setting a bit in the TRISA register puts the correspond-
ing output driver in a hi-impedance mode. Clearing a bit
in the TRISA register puts the contents of the output
latch on the selected pin.
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, this 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.
For the PIC16C924 only, other PORTA pins are multi-
plexed with analog inputs and the analog V
The operation of each pin is selected by clearing/set-
ting the control bits in the ADCON1 register (A/D Con-
trol 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
1997 Microchip Technology Inc.
Note:
STATUS, RP0
STATUS, RP1
PORTA
STATUS, RP0
0xCF
TRISA
PORTS
PORTA and TRISA Register
On a Power-on Reset, these pins are con-
figured as analog inputs and read as '0'.
INITIALIZING PORTA
; Select Bank0
; Initialize PORTA
;
; Value used to
; initialize data
; direction
; Set RA<3:0> as inputs
; RA<5:4> as outputs
; RA<7:6> are always
; read as '0'.
REF
input.
FIGURE 5-1: BLOCK DIAGRAM OF PINS
FIGURE 5-2: BLOCK DIAGRAM OF
Data
bus
WR
Port
WR
TRIS
RD PORT
To A/D Converter (PIC16C924 only)
Note 1: I/O pins have protection diodes to V
Data
bus
WR
TRIS
WR
PORT
RD PORT
Note 1: I/O pin has protection diodes to V
TMR0 clock input
D
D
Data Latch
TRIS Latch
CK
CK
TRIS Latch
Data Latch
D
D
CK
CK
RA3:RA0 AND RA5
RA4/T0CKI PIN
RD TRIS
Q
Q
Q
Q
RD TRIS
Q
Q
Q
Q
PIC16C9XX
Q
Q
EN
Schmitt
Trigger
input
buffer
Analog
input
mode
EN
D
EN
DS30444E - page 31
D
V
N
SS
V
V
P
N
SS
DD
DD
SS
and V
I/O pin
only.
TTL
input
buffer
I/O pin
SS
(1)
.
(1)