MC68HC705JP7 Datasheet, PDF (103/242 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output
Port C (28-Pin Versions Only)
Address: $0006
Bit 7
6
5
4
3
2
1
Bit 0
Read:
DDRC7 DDRC6 DDRC5 DDRC4 DDRC3 DDRC2 DDRC1 DDRC0
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 7-14. Data Direction Register C (DDRC)
DDRC7–DDRC0 — Port C Data Direction Bits
These read/write bits control port C data direction. Reset clears the
DDRC7–DDRC0 bits.
1 = Corresponding port C pin configured as output and pulldown
device disabled
0 = Corresponding port C pin configured as input
7.5.3 Port C Pulldown Devices
All port C pins can have software programmable pulldown devices
enabled or disabled globally by the SWPDI bit in the MOR. These
pulldown devices are individually controlled by the write-only pulldown
register A (PDRA) shown in Figure 7-3. PDICH controls the upper four
pins (PC7–PC4) and PDICL controls the lower four pins (PC3–PC0).
Clearing the PDICH or PDICL bits in the PDRA turns on the pulldown
devices if the port C pin is an input. Reading the PDRA returns undefined
results since it is a write-only register. Reset clears the PDICH and
PDICL bits, which turns on all the port C pulldown devices.
7.5.4 Port C Logic
Figure 7-15 shows the I/O logic of port C.
When a port C pin is programmed as an output, reading the port bit
actually reads the value of the data latch and not the voltage on the pin
itself. When a port C pin is programmed as an input, reading the port bit
reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its DDR bit. Table 7-4 summarizes the
operations of the port C pins.
MC68HC705JJ7 • MC68HC705JP7 — REV 4
MOTOROLA
Parallel Input/Output
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