MC68HC05X4 Datasheet, PDF (49/156 Pages) Motorola, Inc – HCMOS Microcontroller Unit

RESET pin
Freescale Semiconductor, Inc.
Resets, Interrupts and Low Power Modes
Interrupts
When the oscillator is running in a stable state, the MCU is reset when a
logic zero is applied to the RESET input for a minimum period of 1.5
machine cycles (t_CYC). This pin contains an internal Schmitt Trigger as
part of its input to improve noise immunity.
Illegal address
reset
When an opcode fetch occurs from an address which is not part of the
RAM ($0050 – $00FF) or of the NVM ($0F00 – $1F00 and $1FF0 –
$1FFF) then the device is automatically reset.
Computer
operating properly
(COP) reset
The MCU contains a watchdog timer that automatically times out if not
reset (cleared) within a specific time by a program reset sequence. If the
COP watchdog timer is allowed to time-out, an internal reset is
generated to reset the MCU. Because the internal reset signal is used,
the MCU comes out of a COP reset in the same operating mode it was
in when the COP time-out was generated.
The COP reset function is enabled or disabled by a mask option.
Refer to Computer operating properly (COP) watchdog timer for
more information on the COP watchdog timer.
Interrupts
3-resets
MOTOROLA
The MCU can be interrupted by five different sources, four maskable
hardware interrupts and one non-maskable software interrupt:
• MCAN
• Wired-OR function on ports A and B
• Core timer
• 16-bit programmable timer
• Software Interrupt instruction (SWI)
Interrupts cause the processor to save the register contents on the stack
and to set the interrupt mask (I-bit) to prevent additional interrupts. The
Resets, Interrupts and Low Power Modes
For More Information On This Product,
Go to: www.freescale.com
MC68HC05X4 Rev 1.0
49