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313
30.
System Resets
This chapter discusses the System Resets and their associated registers. PSoC devices support several types of resets. The
various resets are designed to provide error-free operation during power up for any voltage ramping profile, to allow for user-
supplied external reset and to provide recovery from errant code operation. For a complete table of the System Reset regis-
ters, refer to the
“Summary Table of the System Resource Registers” on page 272
. For a quick reference of all PSoC registers
in address order, refer to the
Register Details chapter on page 47
30.1
Architectural Description
When reset is initiated, all registers are restored to their
default states. In the
Register Details chapter on page 47
this is indicated by the POR column in the register tables
and elsewhere it is indicated in the Access column, values
on the right side of the colon, in the register tables. Minor
exceptions are explained below.
The following types of resets occur in the PSoC device:
■
Power on Reset (POR). This occurs at low supply volt-
age and is comprised of multiple sources.
■
External Reset (XRES). This active high reset is driven
into the PSoC device, on parts that contain an XRES pin.
■
Watchdog Reset (WDR). This optional reset occurs
when the watchdog timer expires, before being cleared
by user firmware. Watchdog reset defaults to off.
The occurrence of a reset is recorded in the Status and Con-
trol registers (CPU_SCR0 for POR, XRES, and WDR) or in
the System Status and Control Register 1. Firmware can
interrogate these registers to determine the cause of a
reset.
30.2
Pin Behavior During Reset
Power on Reset and External Reset cause toggling on two
GPIO pins, P1[0] and P1[1], as described below and illus-
trated in
. This allows programmers to synchro-
nize with the PSoC device. All other GPIO pins are placed in
a high impedance state during and immediately following
reset.
30.2.1
GPIO Behavior on Power Up
At power up, the internal POR causes P1[0] to initially drive
a strong high (1) while P1[1] drives a resistive low (0). After
256 sleep oscillator cycles (approximately 8 ms), the P1[0]
signal transitions to a resistive low state. After additional 256
sleep oscillator clocks, both pins transition to a high imped-
ance state and normal CPU operation begins. This is illus-
trated in
.
Figure 30-1. P1[1:0] Behavior on Power Up
Internal
Reset
P1[0]
P1[1]
HiZ
HiZ
Vdd
POR Trip
Point
S1
R0
R0
R0
T1
T2
T1 = T2 = 256 Sleep Clock Cycles
(approximately 8 ms)
Summary of Contents for PSoC CY8C23533
Page 4: ...Contents Overview 4 Document 001 20559 Rev D Section G Glossary 385 Index 401 ...
Page 16: ...Contents Overview 16 Document 001 20559 Rev D ...
Page 24: ...24 Document 001 20559 Rev D Section A Overview ...
Page 30: ...30 Document 001 20559 Rev D Pin Information ...
Page 54: ...54 Document 001 20559 Rev D Supervisory ROM SROM ...
Page 60: ...60 Document 001 20559 Rev D RAM Paging ...
Page 68: ...68 Document 001 20559 Rev D Interrupt Controller ...
Page 76: ...12 Document 001 20559 Rev D General Purpose IO GPIO ...
Page 82: ...18 Document 001 20559 Rev D Internal Main Oscillator IMO ...
Page 84: ...20 Document 001 20559 Rev D Internal Low Speed Oscillator ILO ...
Page 90: ...26 Document 001 20559 Rev D External Crystal Oscillator ECO ...
Page 94: ...30 Document 001 20559 Rev D Phase Locked Loop PLL ...
Page 106: ...42 Document 001 20559 Rev D Sleep and Watchdog ...
Page 228: ...164 Document 001 20559 Rev D Section D Digital System ...
Page 234: ...170 Document 001 20559 Rev D Array Digital Interconnect ADI ...
Page 278: ...214 Document 001 20559 Rev D Digital Blocks ...
Page 296: ...232 Document 001 20559 Rev D Analog Interface ...
Page 304: ...240 Document 001 20559 Rev D Analog Array ...
Page 308: ...244 Document 001 20559 Rev D Analog Input Configuration ...
Page 312: ...248 Document 001 20559 Rev D Analog Reference ...
Page 338: ...274 Document 001 20559 Rev D Section F System Resources ...
Page 354: ...290 Document 001 20559 Rev D Multiply Accumulate MAC ...
Page 374: ...310 Document 001 20559 Rev D I2C ...
Page 400: ...336 Document 001 20559 Rev D Section G Glossary ...