Datasheet

© 2006 Microchip Technology Inc. DS30221C-page 33
PIC16F872
4.3 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 4-5). PORTC pins have Schmitt Trigger input
buffers.
When the I
2
C module is enabled, the PORTC (4:3) pins
can be configured with normal I
2
C levels or with SMBus
levels by using the CKE bit (SSPSTAT<6>).
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
the destination should be avoided. The user should
refer to the corresponding peripheral section for the
correct TRIS bit settings.
FIGURE 4-5: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE) RC<2:0>
RC<7:5>
FIGURE 4-6: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE) RC<4:3>
Port/Peripheral Select
(2)
Data Bus
WR
PORT
WR
TRIS
RD
Data Latch
TRIS Latch
RD
Schmitt
Trigger
QD
Q
CK
QD
EN
Peripheral Data Out
0
1
QD
Q
CK
P
N
V
DD
VSS
PORT
Peripheral
OE
(3)
Peripheral Input
I/O pin
(1)
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.
TRIS
Port/Peripheral Select
(2)
Data Bus
WR
PORT
WR
TRIS
RD
Data Latch
TRIS Latch
RD
Schmitt
Trigger
QD
Q
CK
QD
EN
Peripheral Data Out
0
1
QD
Q
CK
P
N
V
DD
Vss
PORT
Peripheral
OE
(3)
SSPl Input
I/O
pin
(1)
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.
0
1
CKE
SSPSTAT<6>
Schmitt
Trigger
with
SMBus
Levels
TRIS