CY8C32_12 CYPRESS [Cypress Semiconductor], CY8C32_12 Datasheet - Page 29

• Manufacturer Part Number: CY8C32_12
• Manufacturer: CYPRESS [Cypress Semiconductor]

Figure 6-3. 32kHzECO Block Diagram
It is recommended that the external 32.768-kHz watch crystal
have a load capacitance (CL) of 6 pF or 12.5 pF. Check the
crystal manufacturer's datasheet. The two external capacitors,
CL1 and CL2, are typically of the same value, and their total
capacitance, CL1CL2 / (CL1 + CL2), including pin and trace
capacitance, should equal the crystal CL value. For more
information, refer to application note
PSoC 5 External
specifications in the
6.1.2.3 Digital System Interconnect
The DSI provides routing for clocks taken from external clock
oscillators connected to I/O. The oscillators can also be
generated within the device in the digital system and Universal
Digital Blocks.
While the primary DSI clock input provides access to all clocking
resources, up to eight other DSI clocks (internally or externally
generated) may be routed directly to the eight digital clock
dividers. This is only possible if there are multiple precision clock
sources.
6.1.3 Clock Distribution
All seven clock sources are inputs to the central clock distribution
system. The distribution system is designed to create multiple
high precision clocks. These clocks are customized for the
design’s requirements and eliminate the common problems
found with limited resolution prescalers attached to peripherals.
The clock distribution system generates several types of clock
trees.

Document Number: 001-56955 Rev. *N
Components
The master clock is used to select and supply the fastest clock
in the system for general clock requirements and clock
synchronization of the PSoC device.
External
(Pin P15[3])
Xi
Crystal Osc
32 kHz
Oscillators. See also pin capacitance
“GPIO”
(Pin P15[2])
32 kHz
crystal
Capacitors
Xo
section on page 72.
XCLK32K
AN54439: PSoC 3 and



Each clock divider consists of an 8-input multiplexer, a 16-bit
clock divider (divide by 2 and higher) that generates ~50 percent
duty cycle clocks, master clock resynchronization logic, and
deglitch logic. The outputs from each digital clock tree can be
routed into the digital system interconnect and then brought back
into the clock system as an input, allowing clock chaining of up
to 32 bits.
6.1.4 USB Clock Domain
The USB clock domain is unique in that it operates largely
asynchronously from the main clock network. The USB logic
contains a synchronous bus interface to the chip, while running
on an asynchronous clock to process USB data. The USB logic
requires a 48 MHz frequency. This frequency can be generated
from different sources, including DSI clock at 48 MHz or doubled
value of 24 MHz from internal oscillator, DSI signal, or crystal
oscillator.
6.2 Power System
The power system consists of separate analog, digital, and I/O
supply pins, labeled VDDA, VDDD, and VDDIOX, respectively. It
also includes two internal 1.8 V regulators that provide the digital
(VCCD) and analog (VCCA) supplies for the internal core logic.
The output pins of the regulators (VCCD and VCCA) and the
VDDIO pins must have capacitors connected as shown in
Figure
as short a trace as possible, and connected to a 1-µF
±10-percent X5R capacitor. The power system also contains a
sleep regulator, an I
Bus Clock 16-bit divider uses the master clock to generate the
bus clock used for data transfers. Bus clock is the source clock
for the CPU clock divider.
Eight fully programmable 16-bit clock dividers generate digital
system clocks for general use in the digital system, as
configured by the design’s requirements. Digital system clocks
can generate custom clocks derived from any of the seven
clock sources for any purpose. Examples include baud rate
generators, accurate PWM periods, and timer clocks, and
many others. If more than eight digital clock dividers are
required, the Universal Digital Blocks (UDBs) and fixed function
Timer/Counter/PWMs can also generate clocks.
Four 16-bit clock dividers generate clocks for the analog system
components that require clocking, such as ADC. The analog
clock dividers include skew control to ensure that critical analog
events do not occur simultaneously with digital switching
events. This is done to reduce analog system noise.
6-4. The two VCCD pins must be shorted together, with
2
PSoC
C regulator, and a hibernate regulator.
®
3: CY8C32 Family
Data Sheet
Page 29 of 122