PIC17C7XX Datasheet, PDF (84/328 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers with 10-bit A/D

PIC17C7XX
10.7 PORTG and DDRG Registers
PORTG is an 8-bit wide bi-directional port. The corre-
sponding data direction register is DDRG. A '1' in
DDRG configures the corresponding port pin as an
input. A '0' in the DDRG register configures the corre-
sponding port pin as an output. Reading PORTG
reads the status of the pins, whereas writing to
PORTG will write to the port latch.
The lower four bits of PORTG are multiplexed with four
channels of the 10-bit A/D converter.
The remaining bits of PORTG are multiplexed with
peripheral output and inputs. RG4 is multiplexed with
the CAP3 input, RG5 is multiplexed with the PWM3
output, RG6 and RG7 are multiplexed with the
USART2 functions.
Upon reset RG3:RG0 is automatically configured as
analog inputs, and must be configured in software to
be a digital I/O.
Example 10-7 shows the instruction sequence to initial-
ize PORTG. 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 10-7: INITIALIZING PORTG
MOVLB
MOVLW
MOVPF
CLRF
MOVLW
MOVWF
5
0x0E
ADCON1
PORTG, F
0x03
DDRG
; Select Bank 5
; Configure PORTG as
; digital
; Initialize PORTG data
; latches before
; the data direction
; register
; Value used to init
; data direction
; Set RG<1:0> as inputs
; RG<7:2> as outputs
FIGURE 10-14: BLOCK DIAGRAM OF RG3:RG0
Data bus
WR PORTG
D
Q
CK Q
Data Latch
WR DDRG
D
Q
CK Q
DDRG Latch
RD PORTG
RD DDRG
Q
D
EENN
VDD
P
I/O pin
N
VSS
ST
input
buffer
VAIN
PCFG3:PCFG0
To other pads
CHS3:CHS0
Note: I/O pins have protection diodes to VDD and VSS.
To other pads
DS30289A-page 84
© 1998 Microchip Technology Inc.