Motorola MC68HC05RC8 User Manual
General Description
Signal Description
MC68HC05RC16 — Rev. 3.0
General Release Specification
MOTOROLA
General Description
23
1.5.1 V
DD
and V
SS
Power is supplied to the microcontroller’s digital circuits using these two
pins. V
pins. V
DD
is the positive supply and V
SS
is ground.
1.5.2 IRQ (Maskable Interrupt Request)
In addition to suppling the EPROM with the required programming
voltage, this pin has a mask option as specified by the user that provides
one of two different choices of interrupt triggering sensitivity. The options
are:
voltage, this pin has a mask option as specified by the user that provides
one of two different choices of interrupt triggering sensitivity. The options
are:
1. Negative edge-sensitive triggering only
2. Both negative edge-sensitive and level-sensitive triggering.
The MCU completes the current instruction before it responds to the
interrupt request. When IRQ goes low for at least one t
interrupt request. When IRQ goes low for at least one t
ILIH
signify that an interrupt has been requested. When the MCU completes
its current instruction, the interrupt latch is tested. If the interrupt latch
contains a logic 1 and the interrupt mask bit (I bit) in the condition code
register is clear, the MCU then begins the interrupt sequence.
its current instruction, the interrupt latch is tested. If the interrupt latch
contains a logic 1 and the interrupt mask bit (I bit) in the condition code
register is clear, the MCU then begins the interrupt sequence.
If the option is selected to include level-sensitive triggering, the IRQ input
requires an external resistor to V
requires an external resistor to V
DD
for wired-OR operation.
The IRQ pin contains an internal Schmitt trigger as part of its input to
improve noise immunity.
improve noise immunity.
Refer to
for more detail.