user manual

General Description

Signal Description

MC68HC05RC16 — Rev. 3.0 General Release Specification

MOTOROLA General Description 23

1.5.1 V

and V

Power is supplied to the microcontroller’s digital circuits using these two

pins. V

is the positive supply and V

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:

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

ILIH

(see 11.8

Control Timing (5.0 Vdc and 2.2 Vdc)), a logic 1 is latched internally to

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

If the option is selected to include level-sensitive triggering, the

IRQ input

requires an external resistor to V

for wired-OR operation.

The

IRQ pin contains an internal Schmitt trigger as part of its input to

improve noise immunity.

Refer to Section 4. Interrupts for more detail.