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Document # 001-20559 Rev. *D
Phase-Locked Loop (PLL)
11.2.1
OSC_CR0 Register
The Oscillator Control Register 0 (OSC_CR0) is used to
configure various features of internal clock sources and
clock nets.
Bit 7: 32k Select.
By default, the 32 kHz clock source is
the Internal Low Speed Oscillator (ILO). Optionally, the
32.768 kHz External Crystal Oscillator (ECO) may be
selected.
Bit 6: PLL Mode.
This is the only bit in the OSC_CR0 reg-
ister that directly influences the Phase-Locked Loop (PLL).
When set, this bit enables the PLL. The EXTCLKEN bit in
the OSC_CR2 register should be set low during PLL opera-
tion.
Bit 5: No Buzz.
Normally, when the Sleep bit is set in the
CPU_SCR register, all PSoC device systems are powered
down, including the bandgap reference. However, to facili-
tate the detection of
POR
and
LVD
events at a rate higher
than the sleep interval, the bandgap circuit is powered up
periodically for about 60
s at the Sleep System Duty Cycle
(set in ECO_TR), which is independent of the sleep interval
and typically higher. When the No Buzz bit is set, the Sleep
System Duty Cycle value is overridden and the bandgap cir-
cuit is forced to be on during sleep. This results in a faster
response to an LVD or POR event (continuous detection as
opposed to periodic detection), at the expense of slightly
higher average sleep current.
Bits 4 and 3: Sleep[1:0].
The available sleep interval
. It must be remembered
that when the ILO is the selected 32 kHz clock source, sleep
intervals are approximate.
Bits 2 to 0: CPU Speed[2:0].
The PSoC M8C may operate
over a range of CPU clock speeds (see
), allowing
the M8C’s performance and power requirements to be tai-
lored to the application.
The reset value for the CPU Speed bits is zero; therefore,
the default CPU speed is one-eighth of the clock source.
The Internal Main Oscillator (IMO) is the default clock
source for the CPU speed circuit; therefore, the default CPU
speed is 3 MHz.
The CPU frequency is changed with a write to the
OSC_CR0 register. There are eight frequencies generated
from a power-of-two divide circuit, which are selected by a
3-bit code. At any given time, the CPU 8-to-1 clock mux is
selecting one of the available frequencies, which is resyn-
chronized to the 24 MHz master clock at the output.
Regardless of the CPU Speed bit’s setting, if the actual CPU
speed is greater than 12 MHz, the 24 MHz operating
requirements apply. An example of this scenario is a device
that is configured to use an external clock, which is supply-
ing a frequency of 20 MHz. If the CPU speed register’s
value is 0b011, the CPU clock is 20 MHz. Therefore, the
supply voltage requirements for the device are the same as
if the part was operating at 24 MHz off of the IMO. The oper-
ating voltage requirements are not relaxed until the CPU
speed is at 12 MHz or less.
Some devices support the slow IMO option, as discussed in
the IMO chapter in the
“Architectural Description” on
. This offers an option to lower both system and
CPU clock speed in order to save power.
An automatic protection mechanism is available for systems
that need to run at peak CPU clock speed but cannot guar-
antee a high enough supply voltage for that clock speed.
See the LVDTBEN bit in the
for more information.
For additional information, refer to the
.
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E0h
32k Select
PLL Mode
No Buzz
Sleep[1:0]
CPU Speed[2:0]
RW : 00
Table 11-1. Sleep Interval Selections
Sleep Interval
OSC_CR[4:3]
Sleep Timer
Clocks
Sleep Period
(nominal)
Watchdog
Period (nominal)
00b (default)
64
1.95 ms
6 ms
01b
512
15.6 ms
47 ms
10b
4096
125 ms
375 ms
11b
32,768
1 sec
3 sec
Table 11-2. OSC_CR0[2:0] Bits: CPU Speed
Bits
6 MHz Internal
Main Oscillator
24 MHz Internal
Main Oscillator
External Clock
000b
750 kHz
3 MHz
EXTCLK/ 8
001b
1.5 MHz
6 MHz
EXTCLK/ 4
010b
3 MHz
12 MHz
EXTCLK/ 2
011b
6 MHz
24 MHz
EXTCLK/ 1
100b
375 kHz
1.5 MHz
EXTCLK/ 16
101b
187.5 kHz
750 kHz
EXTCLK/ 32
110b
93.7 kHz
187.5 kHz
EXTCLK/ 128
111b
46.9 kHz
93.7 kHz
EXTCLK/ 256
Содержание PSoC CY8C23533
Страница 4: ...Contents Overview 4 Document 001 20559 Rev D Section G Glossary 385 Index 401 ...
Страница 16: ...Contents Overview 16 Document 001 20559 Rev D ...
Страница 24: ...24 Document 001 20559 Rev D Section A Overview ...
Страница 30: ...30 Document 001 20559 Rev D Pin Information ...
Страница 54: ...54 Document 001 20559 Rev D Supervisory ROM SROM ...
Страница 60: ...60 Document 001 20559 Rev D RAM Paging ...
Страница 68: ...68 Document 001 20559 Rev D Interrupt Controller ...
Страница 76: ...12 Document 001 20559 Rev D General Purpose IO GPIO ...
Страница 82: ...18 Document 001 20559 Rev D Internal Main Oscillator IMO ...
Страница 84: ...20 Document 001 20559 Rev D Internal Low Speed Oscillator ILO ...
Страница 90: ...26 Document 001 20559 Rev D External Crystal Oscillator ECO ...
Страница 94: ...30 Document 001 20559 Rev D Phase Locked Loop PLL ...
Страница 106: ...42 Document 001 20559 Rev D Sleep and Watchdog ...
Страница 228: ...164 Document 001 20559 Rev D Section D Digital System ...
Страница 234: ...170 Document 001 20559 Rev D Array Digital Interconnect ADI ...
Страница 278: ...214 Document 001 20559 Rev D Digital Blocks ...
Страница 296: ...232 Document 001 20559 Rev D Analog Interface ...
Страница 304: ...240 Document 001 20559 Rev D Analog Array ...
Страница 308: ...244 Document 001 20559 Rev D Analog Input Configuration ...
Страница 312: ...248 Document 001 20559 Rev D Analog Reference ...
Страница 338: ...274 Document 001 20559 Rev D Section F System Resources ...
Страница 354: ...290 Document 001 20559 Rev D Multiply Accumulate MAC ...
Страница 374: ...310 Document 001 20559 Rev D I2C ...
Страница 400: ...336 Document 001 20559 Rev D Section G Glossary ...