UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
53 of 268
NXP Semiconductors
UM10413
MPT612 User manual
When the internal reset is removed, the processor begins executing at address 0, which is
initially the reset vector mapped from the boot block. At that point, all of the processor and
peripheral registers have been initialized to predetermined values.
External and internal resets have some small differences. An external reset causes the
value of certain pins to be latched to configure the part. External circuitry cannot
determine when an internal reset occurs in order to allow setting up those special pins, so
those latches are not reloaded during an internal reset. Pin 26 (RTCK) is examined during
an external reset (see
and
). Pin PIO14
Section 25 “Flash memory system and programming” on page 217
) examines the
on-chip bootloader when this code is executed after every reset.
It is possible for a chip reset to occur during a Flash programming or erase operation. The
Flash memory interrupts the ongoing operation and holds off the completion of reset to the
CPU until internal Flash high voltages have settled.
(1) Reset time: The reset time must be held LOW. This time depends on system parameters such as V
DDC
, V
DD(IO)
rise time, and
the oscillator start-up time. There are no restrictions from the MPT612 except that V
DDC
, V
DD(IO)
, and the oscillator must be
within the specific operating range.
(2) There are no sequencing requirements for V
DD(IO)
and V
DDC
.
(3) When V
DD(IO)
and V
DDC
reach the minimum voltage, a reset is registered within two valid oscillator clocks.
(4) Typical start-up time is 0.5 ms for a 12 MHz crystal.
Fig 13. Start-up sequence diagram
reset time
[1]
clock stability
time
4096 clocks
boot time
jump to user code
1.65 V
[3]
oscillator starts
processor status
reset
V
DDC
V
DD(lO)
oscillator
PLL
lock time
= 100 μs
GND
GND
3.0 V
[3]
V
DD(lO)
, V
DDC
sequencing
(no sequencing requirements)
[2]
0.5 ms
[4]
valid clocks
1000
clocks
SPI
boot
time
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