mc68hc05bs8 Freescale Semiconductor, Inc, mc68hc05bs8 Datasheet - Page 24

• Manufacturer Part Number: mc68hc05bs8
• Description: Mc68hc05 Family Of Low-cost Single-chip Microcontrollers.
• Manufacturer: Freescale Semiconductor, Inc

3
3.2
These are standard M68HC05 bidirectional I/O ports, each comprising a data register and a data
direction register. All three are 8-bit ports.
Reset does not affect the state of the data registers, but clears the data direction registers, thereby
returning all port pins to input mode. Writing a “1” to any DDR sets the corresponding port pin to
output mode.
3.3
In addition to normal I/O function, PB7 can be software selectable to input a reset signal to the
Raster Positioning Pulse Width Modulator counter. The reset pulse requires an active high signal.
3.4
Six keyboard interrupt inputs are available on port pins PC0 to PC5. Each pin is enabled for
keyboard interrupt by setting the corresponding keyboard interrupt enable bit in the KBI register
(bits 0 to 5 of $001E). When the KBI bit is set, the corresponding port C pin will be configured as
an input pin, regardless of the DDRC setting, an internal pull-up resistor is connected to the pin.
3-2
CONNECTIONS
MC68HC05
INTERNAL
Port A, B, and C
PB7 - RSPWM Counter Reset
PC0:5 - Keyboard Interrupts
LATCHED OUTPUT
DATA DIRECTION
REGISTER BIT
DATA BIT
Figure 3-1 Port I/O Circuitry
INPUT/OUTPUT PORTS
REGISTER
INPUT
BIT
INPUT I/O
OUTPUT
MC68HC05BS8
I/O PIN
TPG