PIC17C75X Datasheet, PDF (78/320 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers

PIC17C75X
10.6 PORTF and DDRF Registers
PORTF is an 8-bit wide bi-directional port. The corre-
sponding data direction register is DDRF. A '1' in DDRF
configures the corresponding port pin as an input. A '0'
in the DDRF register configures the corresponding port
pin as an output. Reading PORTF reads the status of
the pins, whereas writing to them will write to the
respective port latch.
All eight bits of PORTF are multiplexed with 8 of the 12
channels of the 10-bit A/D converter.
Upon reset the entire Port is automatically configured
as analog inputs, and must be configured in software to
be a digital I/O.
Example 10-6 shows an instruction sequence to initial-
ize PORTF. The Bank Select Register (BSR) must be
selected to Bank 5 for the port to be initialized. The fol-
lowing example uses the MOVLB instruction to load the
BSR register for bank selection.
EXAMPLE 10-6: INITIALIZING PORTF
MOVLB
MOVLW
MOVPF
CLRF
MOVLW
MOVWF
5
; Select Bank 5
0x0E ; Configure PORTF as
ADCON1 ; Digital
PORTF ; Initialize PORTF data
; latches before setting
; the data direction
; register
0x03 ; Value used to initialize
; data direction
DDRF ; Set RF<1:0> as inputs
; RF<7:2> as outputs
FIGURE 10-13: BLOCK DIAGRAM OF RF7:RF0
Data bus
D
Q
VDD
WR PORTF
CK Q
P
Data Latch
D
Q
N
WR DDRF
CK Q
VSS
DDRF Latch
RD DDRF
RD PORT
VAN
PCFG3:PCFG0
Q
D
EENN
To other pads
I/O pin
ST
input
buffer
CHS3:CHS0
To other pads
DS30264A-page 78
Preliminary
© 1997 Microchip Technology Inc.