PIC17C44-08SLASHP datasheet(58/240 Pages) MICROCHIP

58 / 240 page

PIC17C4X

DS30412C-page 58

9.3

PORTC and DDRC Registers

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.

Note:

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.

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:

INITIALIZING PORTC

MOVLB

;

Select Bank 1

CLRF

PORTC

;

Initialize PORTC data

;

latches before setting

;

the data direction

;

MOVLW

0xCF

;

Value used to initialize

;

data direction

MOVWF

DDRC

;

Set RC<3:0> as inputs

;

RC<5:4> as outputs

;

RC<7:6> as inputs

FIGURE 9-6:

BLOCK DIAGRAM OF RC<7:0> PORT PINS

Note: I/O pins have protection diodes to VDD and Vss.

TTL

Input

Buffer

Port

Data

to D_Bus

→ IR

INSTRUCTION READ

Data Bus

RD_PORTC

WR_PORTC

RD_DDRC

WR_DDRC

EX_EN

DATA/ADDR_OUT

DRV_SYS

SYS BUS

Control

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