User’s Manual 103
9.4 Parallel Port D
Parallel port D, shown in Figure 9-1, has eight pins that can programmed individually to be
inputs and outputs. When programmed as outputs, the pins can be individually selected to be
open-drain outputs or standard outputs. Port D pins can be addressed by bit if desired. The
output registers are cascaded and timer-controlled, making it possible to generate precise
timing pulses. In addition, port D outputs have a higher drive capability. Port D bits 4 and 5
can be used as alternate bits for serial port B, and bits 6 and 7 can be used as alternate bits
for serial port A. Alternate serial port bit assignments make it possible for the same serial
port to connect to different communications lines that are not operating at the same time.
On reset, the data direction register is zeroed, making all pins inputs. In addition bits in the
control register are zeroed (bits 0,1,4,5) to ensure that data is clocked into the output regis-
ters when loaded. All other registers associated with port D are not initialized on reset.
The following registers are described in Table 9-8 and in Table 9-9.
• PDDDR—Parallel port D data direction register. A "1" makes the corresponding pin an
output. Write only.
• PDDCR—Parallel port D drive control register. A "1" makes the corresponding pin an
open-drain output if that pin is set up for output. Write only.
• PDFR—Parallel port D function control register. This port may be used to make port
positions 4 and 6 be serial port outputs. Write only.
Table 9-7. Parallel Port D Registers
Register Name Mnemonic I/O address R/W Reset
Port D Data Register PDDR 0x60 R/W xxxxxxxx
Port D Drive Control Register PDDCR 0x66 W xxxxxxxx
Port D Data Direction Register PDDDR 0x67 W 00000000
Port D Function Register PDFR 0x65 W xxxxxxxx
Port D Control Register PDCR 0x64 W xx00xx00
Port D Bit 0 Register PDB0R 0x68 W xxxxxxxx
Port D Bit 1 Register PDB1R 0x69 W xxxxxxxx
Port D Bit 2 Register PDB2R 0x6A W xxxxxxxx
Port D Bit 3 Register PDB3R 0x6B W xxxxxxxx
Port D Bit 4 Register PDB4R 0x6C W xxxxxxxx
Port D Bit 5 Register PDB5R 0x6D W xxxxxxxx
Port D Bit 6 Register PDB6R 0x6E W xxxxxxxx
Port D Bit 7 Register PDB7R 0x6F W xxxxxxxx
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