Datasheet

Resets and Interrupts
MC9S12DP256 — Revision 1.1
Resets and Interrupts
Figure 12 RESET pin held low externally
For the POR to be rearmed, VDD must fall to V
PORA
or below before the
circuit asserts a power-on reset (see Figure 13). The RESET
pin will be
asserted low until VDD has risen to a level above V
PORR
. At this point
the POR sequence will restart.
An external voltage level detector, or other external reset circuit, is the
usual source of reset in a system. The POR circuit only initializes internal
circuitry during cold starts and cannot be used to force a reset as system
voltage drops. It is important to use an external low voltage reset circuit
(such as an MC33464-48) to prevent power transitions or corruption of
RAM or EEPROM.
Figure 13 POR Re-arm
.
V
PORR
4096 ECLKs
VDD
RESET
Internal POR
Internal RESET
64 ECLKs
32 ECLKs
V
PORA
VDD
V
PORR
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
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