CY8C5468LTI-037 Cypress Semiconductor Corp, CY8C5468LTI-037 Datasheet - Page 20

• Manufacturer Part Number: CY8C5468LTI-037
• Manufacturer: Cypress Semiconductor Corp

Specifications of CY8C5468LTI-037

• Lead Free Status / Rohs Status: Compliant

The central timewheel can be programmed to wake the system
periodically and optionally issue an interrupt. This enables
flexible, periodic wakeups from low power modes or coarse
timing applications. Systems that require accurate timing should
use the Real Time Clock capability instead of the central
timewheel.
The 100 kHz clock (CLK100K) works as a low power system
clock to run the CPU. It can also generate time intervals such as
fast sleep intervals using the fast timewheel.
The fast timewheel is a 100 kHz, 5-bit counter clocked by the ILO
that can also be used to wake the system. The fast timewheel
settings are programmable, and the counter automatically resets
when the terminal count is reached. This enables flexible,
periodic wakeups of the CPU at a higher rate than is allowed
using the central timewheel. The fast timewheel can generate an
optional interrupt each time the terminal count is reached.
The 33 kHz clock (CLK33K) comes from a divide-by-3 operation
on CLK100K. This output can be used as a reduced accuracy
version of the 32.768 kHz ECO clock with no need for a crystal.
6.1.2 External Oscillators
6.1.2.1 MHz External Crystal Oscillator
The MHzECO provides high frequency, high precision clocking
using an external crystal (see
variety of crystal types, in the range of 4 to 25 MHz. When used
in conjunction with the PLL, it can generate CPU and system
clocks up to the device's maximum frequency (see
Phase-Locked Loop
the external crystal and capacitors are fixed. If a crystal is not
used then Xi must be shorted to ground and Xo must be left
floating. MHzECO accuracy depends on the crystal chosen.
Figure 6-2. MHzECO Block Diagram
6.1.2.2 32.768 kHz ECO
The 32.768 kHz External Crystal Oscillator (32kHzECO)
provides precision timing with minimal power consumption using
an external 32.768 kHz watch crystal (see
32kHzECO also connects directly to the sleep timer and provides
the source for the Real Time Clock (RTC). The RTC uses a 1
second interrupt to implement the RTC functionality in firmware.
Document Number: 001-66238 Rev. *A
Components
External
Xi
Crystal Osc
4 - 25 MHz
on page 19). The GPIO pins connecting to
4 – 25 MHz
Capacitors
crystal
XCLK_ MHZ
Xo
Figure
6-2). It supports a wide
Figure
PRELIMINARY
6-3). The
The oscillator works in two distinct power modes. This allows
users to trade off power consumption with noise immunity from
neighboring circuits. The GPIO pins connected to the external
crystal and capacitors are fixed.
Figure 6-3. 32kHzECO Block Diagram
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.
Components
The system clock is used to select and supply the fastest clock
in the system for general system clock requirements and clock
synchronization of the PSoC device.
Bus Clock 16-bit divider uses the system clock to generate the
system’s bus clock used for data transfers and the CPU. The
CPU clock is directly derived from the bus clock.
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.
External
(Pin P15[3])
PSoC
Xi
®
Crystal Osc
32 kHz
5: CY8C54 Family Datasheet
(Pin P15[2])
32 kHz
crystal
Capacitors
Xo
XCLK32K
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