PIC17C752 MICROCHIP [Microchip Technology], PIC17C752 Datasheet - Page 74

• Manufacturer Part Number: PIC17C752
• Description: High-Performance 8-Bit CMOS EPROM Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

10.4
PORTD is an 8-bit bi-directional port. The correspond-
ing data direction register is DDRD. A '1' in DDRD con-
figures the corresponding port pin as an input. A '0' in
the DDRD register configures the corresponding port
pin as an output. Reading PORTD reads the status of
the pins, whereas writing to it will write to the port latch.
PORTD is multiplexed with the system bus. When
operating as the system bus, PORTD is the high order
byte of the address/data bus (AD15:AD8). The timing
for the system bus is shown in the Electrical Character-
istics section.
FIGURE 10-10: BLOCK DIAGRAM OF RD7:RD0 PORT PINS (IN I/O PORT MODE)
DS30264A-page 74
Note: I/O pins have protection diodes to V
Note:
PORTD and DDRD 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.
TTL
Input
Buffer
DD
0
1
and Vss.
Data
Port
Q
Q
R
Preliminary
CK
CK
S
D
D
Example 10-4 shows an instruction sequence to initial-
ize PORTD. 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 10-4: INITIALIZING PORTD
MOVLB
CLRF
MOVLW
MOVWF
1
PORTD
0xCF
DDRD
;
;
;
;
;
;
;
INSTRUCTION READ
;
; Value used to initialize
Initialize PORTD data
latches before setting
the data direction register
data direction
Set RD<3:0> as inputs
RD<5:4> as outputs
RD<7:6> as inputs
Select Bank 1
to D_Bus
DATA/ADDR_OUT
1997 Microchip Technology Inc.
WR_PORTD
RD_PORTD
WR_DDRD
RD_DDRD
DRV_SYS
Data Bus
EX_EN
IR
SYS BUS
Control