22
Document # 001-20559 Rev. *D
External Crystal Oscillator (ECO)
5. The ECO becomes the selected source at the end of the
one-second interval on the edge created by the sleep
interrupt logic. The one-second interval gives the oscilla-
tor time to stabilize before it becomes the active source.
The sleep interrupt need not be enabled for the switch-
over to occur. Reset the sleep timer (if this does not
interfere with any ongoing real-time clock operation), to
guarantee the interval length. Note that the ILO contin-
ues to run until the oscillator is automatically switched
over by the sleep timer interrupt.
6. It is strongly advised to wait the one-second stabilization
period prior to engaging the PLL mode to lock the IMO
frequency to the ECO frequency.
Note 1
The ILO switches back instantaneously by writing
the 32 kHz Select Control bit to ‘0’.
Note 2
If the proper settings are selected in PSoC
Designer, the above steps are automatically done in
boot.asm
.
Note 3
Transitions between oscillator domains may pro-
duce glitches on the 32 kHz clock bus. Functions that
require accuracy on the 32 kHz clock should be enabled
after the transition in oscillator domains.
10.1.1
ECO External Components
The external component connections and selections of the
External Crystal Oscillator are illustrated in
■
Crystal – 32.768 kHz watch crystal such as Epson C-
002RX.
■
Capacitors – C1, C2 use NPO ceramic caps.
Use the equation below if you do not employ PLL mode.
C1 = C2 = 25 pF - (Package Capacitance) -
(Board Parasitic Capacitance)
An error of 1 pF in C1 and C2 gives about a 3 ppm error in
frequency.
Figure 10-2. 20-Pin Example of the ECO External
Connections
Refer to the device data sheet, in the packaging chapter, for
typical package capacitances on crystal pins.
10.2
PSoC Device Distinctions
Bits 3 and 2 (ECO EXW and ECO EX, respectively) in the
CPU_SCR1 register cannot be used by the CY8C27x43 for
silicon revision A, and by the CY8C24533, CY8C23533,
CY8C23433, CY8C24633, CY8C24x23, and CY8C22x13
PSoC devices.
C3
PSoC
Vdd
Vss
P1[1]
P1[0]
X1
Vss
Vdd
Vdd
C1
C2
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 ...