PIC16F870/871
3.3
PORTC and the TRISC Register
PORTC is an 8-bit wide, bi-directional port. The corre-
sponding data direction register is TRISC. Setting a
TRISC bit (=1) will make the corresponding PORTC pin
an input (i.e., put the corresponding output driver in a
hi-impedance mode). Clearing a TRISC bit (=0) will
make the corresponding PORTC pin an output (i.e., put
the contents of the output latch on the selected pin).
PORTC is multiplexed with several peripheral functions
(Table 3-5). PORTC pins have Schmitt Trigger input
buffers.
When enabling peripheral functions, care should be
taken in defining TRIS bits for each PORTC pin. Some
peripherals override the TRIS bit to make a pin an out-
put, while other peripherals override the TRIS bit to
make a pin an input. Since the TRIS bit override is in
effect while the peripheral is enabled, read-modify-
write instructions (BSF, BCF, XORWF) with TRISC as
destination should be avoided. The user should refer to
the corresponding peripheral section for the correct
TRIS bit settings.
FIGURE 3-5: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE)
PORT/PERIPHERAL Select(2)
Peripheral Data Out
VDD
0
Data Bus
D
Q
Q
P
WR
1
PORT
CK
Data Latch
I/O
pin(1)
D
Q
Q
WR
TRIS
CK
N
TRIS Latch
VSS
Schmitt
Trigger
RD TRIS
Peripheral
OE(3)
Q
D
EN
RD
PORT
Peripheral Input
Note 1: I/O pins have diode protection to VDD and VSS.
2: Port/Peripheral select signal selects between port
data and peripheral output.
3: Peripheral OE (output enable) is only activated if
peripheral select is active.
1999 Microchip Technology Inc.
Preliminary
DS30569A-page 31
MICROCHIP [ MICROCHIP ]
