PIC17C42 Microchip Technology, PIC17C42 Datasheet - Page 58

• Manufacturer Part Number: PIC17C42
• Description: High-Performance 8-Bit CMOS EPROM/ROM Microcontroller
• Manufacturer: Microchip Technology

PIC17C4X
9.3
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 it 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 timing for
the system bus is shown in the Electrical Characteris-
tics section.
FIGURE 9-6:
DS30412C-page 58
Note: I/O pins have protection diodes to V
Note:
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 gen-
eral purpose I/O.
BLOCK DIAGRAM OF RC<7:0> PORT PINS
TTL
Input
Buffer
DD
0
1
and Vss.
Data
Port
Q
Q
R
CK
CK
S
D
D
Example 9-2 shows the instruction sequence to initial-
ize PORTC. The Bank Select Register (BSR) must be
selected to Bank 1 for the port to be initialized.
EXAMPLE 9-2:
MOVLB 1
CLRF
MOVLW 0xCF
MOVWF DDRC
PORTC
INSTRUCTION READ
INITIALIZING PORTC
;
;
;
;
;
;
;
;
;
;
to D_Bus
DATA/ADDR_OUT
1996 Microchip Technology Inc.
Select Bank 1
Initialize PORTC data
Value used to initialize
Set RC<3:0> as inputs
data direction
latches before setting
the data direction
register
RC<5:4> as outputs
RC<7:6> as inputs
WR_PORTC
RD_PORTC
WR_DDRC
RD_DDRC
DRV_SYS
Data Bus
EX_EN
IR
SYS BUS
Control