CY8C5246AXI-038 Cypress Semiconductor Corp, CY8C5246AXI-038 Datasheet - Page 19

• Manufacturer Part Number: CY8C5246AXI-038
• Manufacturer: Cypress Semiconductor Corp

Specifications of CY8C5246AXI-038

• Lead Free Status / RoHS Status: Compliant

a mechanism for generating clock frequencies based upon a
variety of input sources. The PLL outputs clock frequencies in
the range of 24 to 40 MHz. Its input and feedback dividers supply
4032 discrete ratios to create almost any desired system clock
frequency. The accuracy of the PLL output depends on the
accuracy of the PLL input source. The most common PLL use is
to multiply the IMO clock at 3 MHz, where it is most accurate, to
generate the CPU and system clocks up to the device’s
maximum frequency.
The PLL achieves phase lock within 250 µs (verified by bit
setting). It can be configured to use a clock from the IMO,
MHzECO, or DSI (external pin). The PLL clock source can be
used until lock is complete and signaled with a lock bit. The lock
signal can be routed through the DSI to generate an interrupt.
Disable the PLL before entering low power modes.
6.1.1.4 Internal Low Speed Oscillator
The ILO provides clock frequencies for low power consumption,
including the watchdog timer, and sleep timer. The ILO
generates up to three different clocks: 1 kHz, 33 kHz, and
100 kHz.
The 1-kHz clock (CLK1K) is typically used for a background
‘heartbeat’ timer. This clock inherently lends itself to low power
supervisory operations such as the watchdog timer and long
sleep intervals using the central timewheel (CTW). The central
timewheel is a 1-kHz, free-running, 13-bit counter clocked by the
ILO. The central timewheel is always enabled except in
hibernate mode and when the CPU is stopped during debug on
chip mode. It can be used to generate periodic interrupts for
timing purposes or to wake the system from a low power mode.
Firmware can reset the central timewheel.
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 RTC 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 33 MHz. When used
in conjunction with the PLL, it can generate CPU and system
clocks up to the device's maximum frequency (see
Speed
crystal and capacitors are fixed. MHzECO accuracy depends on
the crystal chosen.
Document Number: 001-55034 Rev. *G
Oscillator). The GPIO pins connecting to the external
Figure
6-2). It supports a wide
PRELIMINARY
Internal Low
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 RTC. The RTC uses a 1-second interrupt to
implement the RTC functionality in firmware.
The oscillator works in two distinct power modes. This allows you
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 UDBs.
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.
Components
Components
External
External
(Pin P15[3])
(Pin P15[1])
PSoC
Xi
Xi
®
Crystal Osc
Crystal Osc
4 - 33 MHz
32 kHz
5: CY8C52 Family Datasheet
(Pin P15[2])
(Pin P15[0])
32 kHz
4 – 33 MHz
crystal
Capacitors
Capacitors
crystal
XCLK_MHZ
Xo
Xo
XCLK32K
Figure
6-3). The
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