Datasheet

 1997 Microchip Technology Inc. DS30444E - page 35
PIC16C9XX
5.3 PORTC and TRISC Register
PORTC is an 6-bit bi-directional port. Each pin is indi-
vidually configurable as an input or output through the
TRISC register. PORTC is multiplexed with several
peripheral functions (Table 5-5). 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-mod-
ify-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.
EXAMPLE 5-3: INITIALIZING PORTC
BCF STATUS,RP0 ; Select Bank0
BCF STATUS,RP1
CLRF PORTC ; Initialize PORTC
BSF STATUS,RP0 ;
MOVLW 0xCF ; Value used to
; initialize data
; direction
MOVWF TRISC ; Set RC<3:0> as inputs
; RC<5:4> as outputs
; RC<7:6> always read 0
FIGURE 5-5: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE)
Data Latch
RBPU
(2)
P
V
DD
QD
CK
QD
CK
Q D
EN
Data bus
WR Port
WR TRIS
RD TRIS
RD Port
weak
pull-up
RD Port
RB0/INT
I/O
pin
(1)
TTL
Input
Buffer
Note 1: I/O pins have diode protection to V
DD and VSS.
2: To enable weak pull-ups, set the appropriate TRIS bit(s)
and clear the RBPU bit (OPTION<7>).
Schmitt Trigger
Buffer
TRIS Latch
TABLE 5-5: PORTC FUNCTIONS
TABLE 5-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC
Name Bit# Buffer Type Function
RC0/T1OSO/T1CKI bit0 ST Input/output port pin or Timer1 oscillator output or Timer1 clock input
RC1/T1OSI bit1 ST Input/output port pin or Timer1 oscillator input
RC2/CCP1 bit2 ST Input/output port pin or Capture input/Compare output/PWM output
RC3/SCK/SCL bit3 ST Input/output port pin or the synchronous serial clock for both SPI and
I
2
C modes.
RC4/SDI/SDA bit4 ST Input/output port pin or the SPI Data In (SPI mode) or data I/O (I
2
C
mode).
RC5/SDO bit5 ST Input/output port pin or Synchronous Serial Port data out
Legend: ST = Schmitt Trigger input
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
Power-on
Reset
Value on all
other resets
07h PORTC — — RC5 RC4 RC3 RC2 RC1 RC0 --xx xxxx --uu uuuu
87h TRISC — — PORTC Data Direction Control Register --11 1111 --11 1111
Legend: x = unknown, u = unchanged, - = unimplemented, read as '0'. Shaded cells are not used by PORTC.