
2001 Microchip Technology Inc.
DS30292C-page 33
PIC16F87X
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
buffers.
When the I2C module is enabled, the PORTC<4:3>
pins can be configured with normal I2C 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
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) RC<2:0>,
RC<7:5>
FIGURE 3-6:
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
Q
D
Q
CK
QD
EN
Peripheral Data Out
0
1
Q
D
Q
CK
P
N
VDD
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
Q
D
Q
CK
QD
EN
Peripheral Data Out
0
1
Q
D
Q
CK
P
N
VDD
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