16
Document # 001-20559 Rev. *D
Internal Main Oscillator (IMO)
8.3
Register Definitions
The following registers are associated with the Internal Main Oscillator (IMO). The register descriptions have an associated
register table showing the bit structure for that register. The bits in the tables that are grayed out are reserved bits and are not
detailed in the register descriptions that follow. Reserved bits should always be written with a value of ‘0’. For a complete table
showing all oscillator registers, refer to the
“Summary Table of the Core Registers” on page 32
8.3.1
CPU_SCR1 Register
The System Status and Control Register 1 (CPU_SCR1) is
used to convey the status and control of events related to
internal resets and watchdog reset.
Bit 7: IRESS.
The Internal Reset Status bit is a read only bit
that may be used to determine if the booting process
occurred more than once.
When this bit is set, it indicates that the SROM SWBootRe-
set code was executed more than once. If this bit is not set,
the SWBootReset executed only once. In either case, the
SWBootReset code does not allow execution from code
stored in Flash until the M8C Core is in a safe operating
mode with respect to supply voltage and Flash operation.
There is no need for concern when this bit is set. It is pro-
vided for systems which may be sensitive to boot time, so
that they can determine if the normal one-pass boot time is
exceeded. For more information on the SWBootReest code
see the
Supervisory ROM (SROM) chapter on page 45
Bit 4: SLIMO.
When set, the Slow IMO bit allows the active
power dissipation of the PSoC device to be reduced by
slowing down the IMO from 24 MHz to 6 MHz. The IMO trim
value must also be changed when SLIMO is set. When not
in external clocking mode, the IMO is the source for SYS-
CLK; therefore, when the speed of the IMO changes, so
does SYSCLK.
Bit 3: ECO EXW.
The ECO Exists Written bit is used as a
status bit to indicate that the ECO EX bit has been previ-
ously written to. It is read only. When this bit is a ‘1’, this indi-
cates that the CPU_SCR1 register has been written to and
is now locked. When this bit is a ‘0’, the register has not
been written to since the last reset event. Note that this bit
cannot be used by the CY8C27x43 for silicon revision A,
and by the CY8C24533, CY8C23533, CY8C23433,
CY8C24633, CY8C24x23, and CY8C22x13 PSoC devices.
Bit 2: ECO EX.
The ECO Exists bit serves as a flag to the
hardware, to indicate that an external crystal
exists in the system. Just after boot, it may be written
only
once
to a value of ‘1’ (crystal exists) or ‘0’ (crystal does not
exist). If the bit is ‘0’, a switch-over to the ECO is locked out
by hardware. If the bit is ‘1’, hardware allows the firmware to
freely switch between the ECO and ILO. It should be written
as early as possible after a
or
event, where it is assumed that pro-
gram execution integrity is high. Note that this bit cannot be
used by the CY8C27x43 for silicon revision A, and by the
CY8C24533, CY8C23533, CY8C23433, CY8C24633,
CY8C24x23, and CY8C22x13 PSoC devices.
Bit 0: IRAMDIS.
The Initialize RAM Disable bit is a control
bit that is readable and writeable. The
for this
bit is ‘0’, which indicates that the maximum amount of SRAM
should be initialized on watchdog reset to a value of 00h.
When the bit is ‘1’, the minimum amount of SRAM is initial-
ized after a watchdog reset. For more information on this bit,
see the
“SROM Function Descriptions” on page 46
.
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
x,FEh
IRESS
SLIMO
ECO EXW *
ECO EX *
IRAMDIS
# : 00
LEGEND
x
An “x” before the comma in the address field indicates that this register can be read or written to no matter what bank is used.
# Access is bit specific. Refer to the
Register Details chapter on page 47
for additional information.
*
Bits 3 and 2 (ECO EXW and ECO EX, respectively) cannot be used by the CY8C27x43 for silicon revision A, and by the CY8C24533, CY8C23533,
CY8C23433, CY8C24633, CY8C24x23, and CY8C22x13 PSoC devices.
Summary of Contents for PSoC CY8C23533
Page 4: ...Contents Overview 4 Document 001 20559 Rev D Section G Glossary 385 Index 401 ...
Page 16: ...Contents Overview 16 Document 001 20559 Rev D ...
Page 24: ...24 Document 001 20559 Rev D Section A Overview ...
Page 30: ...30 Document 001 20559 Rev D Pin Information ...
Page 54: ...54 Document 001 20559 Rev D Supervisory ROM SROM ...
Page 60: ...60 Document 001 20559 Rev D RAM Paging ...
Page 68: ...68 Document 001 20559 Rev D Interrupt Controller ...
Page 76: ...12 Document 001 20559 Rev D General Purpose IO GPIO ...
Page 82: ...18 Document 001 20559 Rev D Internal Main Oscillator IMO ...
Page 84: ...20 Document 001 20559 Rev D Internal Low Speed Oscillator ILO ...
Page 90: ...26 Document 001 20559 Rev D External Crystal Oscillator ECO ...
Page 94: ...30 Document 001 20559 Rev D Phase Locked Loop PLL ...
Page 106: ...42 Document 001 20559 Rev D Sleep and Watchdog ...
Page 228: ...164 Document 001 20559 Rev D Section D Digital System ...
Page 234: ...170 Document 001 20559 Rev D Array Digital Interconnect ADI ...
Page 278: ...214 Document 001 20559 Rev D Digital Blocks ...
Page 296: ...232 Document 001 20559 Rev D Analog Interface ...
Page 304: ...240 Document 001 20559 Rev D Analog Array ...
Page 308: ...244 Document 001 20559 Rev D Analog Input Configuration ...
Page 312: ...248 Document 001 20559 Rev D Analog Reference ...
Page 338: ...274 Document 001 20559 Rev D Section F System Resources ...
Page 354: ...290 Document 001 20559 Rev D Multiply Accumulate MAC ...
Page 374: ...310 Document 001 20559 Rev D I2C ...
Page 400: ...336 Document 001 20559 Rev D Section G Glossary ...