PIC17C756A MICROCHIP [Microchip Technology], PIC17C756A Datasheet - Page 80

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

PIC17C7XX
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 PORTD 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
Specifications section.
FIGURE 10-10:
DS30289B-page 80
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.
BLOCK DIAGRAM OF RD7:RD0 PORT PINS (IN I/O PORT MODE)
TTL
Input
Buffer
DD
0
1
and V
Port
Data
SS
.
Q
Q
R
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:
MOVLB
CLRF
MOVLW
MOVWF
1
PORTD, F
0xCF
DDRD
INSTRUCTION READ
; Select Bank 1
; Initialize PORTD data
; latches before setting
; the data direction reg
; Value used to initialize
; data direction
; Set RD<3:0> as inputs
; RD<5:4> as outputs
; RD<7:6> as inputs
INITIALIZING PORTD
DATA/ADDR_OUT
To D_Bus
2000 Microchip Technology Inc.
WR_PORTD
RD_PORTD
WR_DDRD
RD_DDRD
DRV_SYS
Data Bus
EX_EN
IR
System Bus
Control