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CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
System Resets
30.4
Timing Diagrams
30.4.1
Power On Reset
A Power on Reset (POR) is triggered whenever the supply
voltage is below the POR trip point. POR ends when the
supply voltage rises above this voltage. Refer to the
operation of the POR block.
POR consists of two pieces: an imprecise POR (IPOR) and
a Precision POR (PPOR). “POR” refers to the OR of these
two functions. IPOR has coarser accuracy and its trip point
is typically lower than PPOR’s trip point. PPOR is derived
from a circuit that is calibrated (during boot), for a very accu-
rate location of the POR trip point.
During POR (POR=1), the IMO is powered off for low power
during start-up. After POR deasserts, the IMO is started (see
POR configures register reset status bits as shown in
. PPOR does not affect the BandGap Trim regis-
ter (BDG_TR), but IPOR does reset this register.
30.4.2
External Reset
An External Reset (XRES) is caused by pulling the XRES
pin high. The XRES pin has an always-on, pull down resis-
tor, so it does not require an external pull down for operation
and can be tied directly to ground or left open. Behavior after
XRES is similar to POR.
During XRES (XRES = 1), the IMO is powered off for low
power during start-up. After XRES deasserts, the IMO is
started (see
). How the XRES configures register
reset status bits is shown in
.
30.4.3
Watchdog Timer Reset
The user has the option to enable the Watchdog Timer
Reset (WDR), by clearing the PORS bit in the CPU_SCR0
register. When the PORS bit is cleared, the watchdog timer
cannot be disabled. The only exception to this is if a POR/
XRES event takes place, which will disable the WDR. Note
that a WDR does not clear the Watchdog timer. See
for details of the Watchdog opera-
tion.
When the watchdog timer expires, a watchdog event occurs
resulting in the reset sequence. Some characteristics unique
to the WDR are as follows.
■
PSoC device reset asserts for one cycle of the CLK32K
clock (at its reset state).
■
The IMO is not halted during or after WDR (that is, the
part does not go through a low power phase).
■
CPU operation restarts one CLK32K cycle after the inter-
nal reset deasserts (see
).
How the WDR configures register reset status bits is shown
in
.
Figure 30-3. Key Signals During WDR and IRES
CLK32
Reset
Sleep Timer
IMO PD
IMO (not to scale)
CPU Reset
0
1
2
N=2048
IRES
: Reset 1 cycle, then 2048 additional cycles low power hold-off, and then 1
cycle with IMO on before the CPU reset is released.
WDR
: Reset 1 cycle, then one additional cycle before the CPU reset is released.
IMO PD
IMO (not to scale)
CPU Reset
(Stays low)
Reset
Sleep Timer
0
1
2
CLK32
Содержание CY8C28 series
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Страница 85: ...84 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Internal Main Oscillator IMO ...
Страница 93: ...92 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G External Crystal Oscillator ECO ...
Страница 97: ...96 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Phase Locked Loop PLL ...
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Страница 425: ...424 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Analog Reference ...
Страница 461: ...460 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Two Column Limited Analog System ...
Страница 477: ...476 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Digital Clocks ...
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Страница 513: ...512 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Internal Voltage Reference ...
Страница 523: ...522 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Switch Mode Pump SMP ...
Страница 533: ...532 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G I O Analog Multiplexer ...
Страница 537: ...536 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G Real Time Clock RTC ...
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