General Description

Signal Description

1.5.1 VDD and VSS

Power is supplied to the microcontroller’s digital circuits using these two pins. VDD is the positive supply and VSS 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 tILIH (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 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 VDD 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.

MC68HC05RC16 — Rev. 3.0

 

General Release Specification

 

 

 

MOTOROLA

General Description

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