PIC17C756A MICROCHIP [Microchip Technology], PIC17C756A Datasheet - Page 78

• Manufacturer Part Number: PIC17C756A
• Description: High-Performance 8-bit CMOS EPROM Microcontrollers with 10-bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC17C7XX
10.3
PORTC is an 8-bit bi-directional port. The correspond-
ing data direction register is DDRC. A ’1’ in DDRC con-
figures the corresponding port pin as an input. A ’0’ in
the DDRC register configures the corresponding port
pin as an output. Reading PORTC reads the status of
the pins, whereas writing to PORTC will write to the port
latch. PORTC is multiplexed with the system bus.
When operating as the system bus, PORTC is the low
order byte of the address/data bus (AD7:AD0). The tim-
ing for the system bus is shown in the Electrical Speci-
fications section.
FIGURE 10-9:
DS30289B-page 78
Note:
Note: I/O pins have protection diodes to V
PORTC and DDRC Registers
This port is configured as the system bus
when the device’s configuration bits are
selected to Microprocessor or Extended
Microcontroller modes. In the two other
microcontroller modes, this port is a
general purpose I/O.
BLOCK DIAGRAM OF RC7:RC0 PORT PINS
TTL
Input
Buffer
DD
0
1
and V
Data
Port
SS
.
Q
Q
R
CK
CK
S
D
D
Example 10-3 shows an instruction sequence to initial-
ize PORTC. The Bank Select Register (BSR) must be
selected to Bank 1 for the port to be initialized. The fol-
lowing example uses the MOVLB instruction to load the
BSR register for bank selection.
EXAMPLE 10-3:
MOVLB
CLRF
MOVLW
MOVWF
1
PORTC, F
0xCF
DDRC
INSTRUCTION READ
; Select Bank 1
; Initialize PORTC data
; latches before setting
; the data direction reg
; Value used to initialize
; data direction
; Set RC<3:0> as inputs
; RC<5:4> as outputs
; RC<7:6> as inputs
INITIALIZING PORTC
DATA/ADDR_OUT
To D_Bus
2000 Microchip Technology Inc.
WR_PORTC
RD_PORTC
WR_DDRC
RD_DDRC
DRV_SYS
Data Bus
EX_EN
IR
System Bus
Control