PIC16F87X
3.3
PORTC and the TRISC Register
FIGURE 3-6: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
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).
OVERRIDE) RC<3:4>
PORT/PERIPHERAL Select(2)
Peripheral Data Out
VDD
0
Data Bus
D
Q
Q
P
WR
1
PORT
CK
PORTC is multiplexed with several peripheral functions
(Table 3-5). PORTC pins have Schmitt Trigger input
buffers.
When the I2C module is enabled, the PORTC (3:4) pins
can be configured with normal I2C levels or with
SMBUS levels by using the CKE bit (SSPSTAT <6>).
Data Latch
I/O
pin(1)
D
Q
Q
WR
TRIS
CK
N
TRIS Latch
Vss
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.
Schmitt
Trigger
RD TRIS
Peripheral
OE(3)
Q
D
Schmitt
Trigger
with
SMBus
levels
EN
RD
PORT
0
SSPl Input
1
CKE
SSPSTAT<6>
Note 1: I/O pins have diode protection to VDD and VSS.
2: Port/Peripheral select signal selects between port
data and peripheral output.
FIGURE 3-5: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE) RC<0:2>
RC<5:7>
3: Peripheral OE (output enable) is only activated if
peripheral select is active.
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.
DS30292B-page 33
ETC [ ETC ]
