XC68HC705F32 Motorola, XC68HC705F32 Datasheet - Page 46

• Manufacturer Part Number: XC68HC705F32
• Description: MICROCONTROLLER
• Manufacturer: Motorola

4
4.2
Port A is an 8-bit bidirectional port which is equipped with a keyboard interrupt. All eight lines have
internal pull-up resistors, which are required when the port is in input mode. On reset, this port is
configured as a standard I/O port comprising a data register and a data direction register.
Reset does not affect the state of the data register, but clears the data direction register, thereby
returning all ports pins to input mode. Writing a 1 to any DDR bit sets the corresponding port pin
to output mode. As every pin configured as an input contributes to the keyboard interrupt, it is
possible to disable a single pin by configuring it as an output.
4.2.1
Provided that the interrupt mask bit of the condition code register is cleared, the keyboard interrupt
facility is enabled by setting the keyboard interrupt bit (KIE) in the key control register.
On detection of a high-to-low transition, the interrupt inputs PA6 and PA7 are triggered. The trigger
edges of the interrupt lines, PA0–PA5, can be programmed using the EDG0–EDG5 bits in the key
control register. If one of these bits is cleared, after reset the corresponding interrupt is falling-edge
sensitive. If, however, one of them is set, after reset the corresponding interrupt is rising-edge
sensitive. The internal pull-up resistors of input lines, PA7–PA0, are disabled, if rising-edge
sensitivity is selected.
When a correct transition is detected, on any of this port’s pins, a keyboard interrupt request is
generated, and the corresponding interrupt status flag of the interrupt status register, IRSTATE, is
set. The interrupt status register is an 8-bit register which has the same address as PORTA,
$0000. This register can be read if the KEYMUX bit in the system option register is set. If KIE is
set, a keyboard interrupt is generated and the keyboard status flag, KF, is set by generating the
logical OR of the eight interrupt state register outputs.
The 8 interrupt state register flags can be reset in three ways:
MOTOROLA
4-2
1) Completely, if the chip is reset.
2) Completely, if a 1 is written to KEYCLR, in the system option register.
3) Individually, if a 1 is written to the corresponding bit position of the interrupt
state register ($00 with KEYMUX = 1, in the system option register).
Port A
Keyboard interrupt
PARALLEL INPUT/OUTPUT PORTS
MC68HC05F32
TPG