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CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
System Resets
30.3
Register Definitions
The following registers are associated with the PSoC System Resets and are listed in address order. Each register descrip-
tion has 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 of system reset registers, refer to the
“Summary Table of the System Resource Registers” on
30.3.1
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 was executed only once. In either case,
the SWBootReset code will 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
was exceeded. For more information on the SWBootReest
code see the
Supervisory ROM (SROM) chapter on
.
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 (see
“Engaging Slow IMO” on page 81
). When not in external
clocking mode, the IMO is the source for SYSCLK; there-
fore, when the speed of the IMO changes, so will 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.
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.
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 50
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
Содержание CY8C28 series
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Страница 93: ...92 CY8C28xxx PSoC Programmable System on Chip TRM Document No 001 52594 Rev G External Crystal Oscillator ECO ...
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