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enCoRe™ V CY7C643xx, enCoRe™ V LV CY7C604xx TRM, Document No. 001-32519 Rev *H
96
14. Digital Clocks
This chapter discusses the Digital Clocks and their associated registers. It serves as an overview of the clocking options
available in the enCoRe V devices. For detailed information on specific oscillators, see the individual oscillator chapters in the
section called
. For a complete table of the digital clock registers, refer to the
. For a quick reference of all enCoRe V registers in address order, refer to the
.
14.1
Architectural Description
The enCoRe V M8C core has a large number of clock
sources that increase the flexibility of the enCoRe V device,
as listed in
14.1.1
Internal Main Oscillator
The Internal Main Oscillator (IMO) is the foundation upon
which almost all other clock sources in the enCoRe V device
are based. The default mode of the IMO creates a 12 MHz
reference clock that is used by many other circuits in the
device. The enCoRe V device has an option to replace the
IMO with an externally supplied clock that becomes the
base for all of the clocks the IMO normally serves. The inter-
nal base clock net is called SYSCLK and is driven by either
the IMO or an external clock (EXTCLK).
Whether the external clock or the internal main oscillator is
selected, all device functions are clocked from a derivative
of SYSCLK or are resynchronized to SYSCLK. All external
asynchronous signals and the internal low-speed oscillator
are resynchronized to SYSCLK for use in the digital blocks.
The IMO frequency can be adjusted to other frequencies
besides 12 MHz. See the
for more information.
The IMO is discussed in detail in the
14.1.2
Internal Low-speed Oscillator
The Internal Low-speed Oscillator (ILO) is available as a
general clock, but is also the clock source for the sleep and
watchdog timers. The ILO can be disabled in deep sleep
mode, or in other sleep modes when the ECO is enabled.
The ILO is discussed in detail in the
Oscillator (ILO) chapter on page 72
.
Table 14-1. System Clocking Signals and Definitions
Signal
Definition
SYSCLK
Either the direct output of the Internal Main Oscillator or the
direct input of the EXTCLK pin while in external clocking
mode.
CPUCLK
SYSCLK is divided down to one of eight possible frequencies
to create CPUCLK, which determines the speed of the M8C.
See the
CLK32K
The Internal Low-speed Oscillators output. See the
CLKIM0
The internally generated clock from the IMO. By default, this
clock drives SYSCLK; however, an external clock may be
used by enabling EXTCLK mode. The IMO can be set to var-
ious frequencies; the default is 12 MHz.
SLEEP
One of four sleep intervals may be selected from 1.95 ms to 1
second. See the