MC68HC05L28 Datasheet, PDF (28/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

2.2
Pin descriptions
2
Pin assignments are shown in Section 13.
2.2.1 VDD and VSS
Power is supplied to the microcontroller using these two pins. VDD is the positive supply and VSS
is ground.
It is in the nature of CMOS designs that very fast signal transitions occur on the MCU pins. These
short rise and fall times place very high short-duration current demands on the power supply. To
prevent noise problems, special care must be taken to provide good power supply bypassing at
the MCU. Bypass capacitors should have good high-frequency characteristics and be as close to
the MCU as possible. Bypassing requirements vary, depending on how heavily the MCU pins are
loaded.
2.2.2 IRQ0
This interrupt has a software option which offers two types of interrupt triggering sensitivity. It
contains an internal Schmitt trigger as part of its input to improve noise immunity.
2.2.3 IRQ1
This interrupt has a software option which offers four types of interrupt triggering sensitivity. It
contains an internal Schmitt trigger as part of its input to improve noise immunity. This interrupt can
be enabled/disabled independently.
2.2.4 IRQ2
This interrupt has a software option which offers four types of interrupt triggering sensitivity. It
contains an internal Schmitt trigger as part of its input to improve noise immunity. This interrupt can
be enabled/disabled independently.
MOTOROLA
2-6
MODES OF OPERATION AND PIN DESCRIPTIONS
TPG
MC68HC05L28