enCoRe™ V CY7C643xx, enCoRe™ V LV CY7C604xx TRM, Document No. 001-32519 Rev *H
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System Resets
16.3.2
CPU_SCR0 Register
The System Status and Control Register 0 (CPU_SCR0) is
used to convey the status and control of events for various
functions of a enCoRe V device.
Bit 7: GIES.
Global Interrupt Enable Status. This bit is a
read-only status bit and its use is discouraged. The GIES bit
is a legacy bit that was used to provide the ability to read the
GIE bit of the CPU_F register. However, the CPU_F register
is now readable. When this bit is set, it indicates that the GIE
bit in the CPU_F register is also set, which in turn, indicates
that the microprocessor services interrupts.
Bit 5: WDRS.
WatchDog Reset Status. This bit may not be
set. It is normally ‘0’ and automatically set whenever a
watchdog reset occurs. The bit is readable and clearable by
writing a ‘0’ to its bit position in the CPU_SCR0 register.
Bit 4: PORS.
Power-on-reset Status. This bit, which is the
watchdog enable bit, is set automatically by a POR or
XRES. If the bit is cleared by user code, the watchdog timer
is enabled. After cleared, the only way to reset the PORS bit
is to go through a POR or XRES. Thus, there is no way to
disable the watchdog timer other than to go through a POR
or XRES.
Bit 3: Sleep.
This bit is used to enter Low-power Sleep
mode when set. To wake up the system, this register bit is
cleared asynchronously by any enabled interrupt. Two spe-
cial features of this bit ensure proper sleep operation. First,
the write to set the register bit is blocked if an interrupt is
about to be taken on that instruction boundary (immediately
after the write). Second, there is a hardware interlock to
ensure that, when set, the SLEEP bit may not be cleared by
an incoming interrupt until the sleep circuit has finished per-
forming the sleep sequence and the system-wide power
down signal is asserted. This prevents the sleep circuit from
being interrupted in the middle of the process of system
power down, possibly leaving the system in an indetermi-
nate state.
Bit 0: STOP.
This bit is readable and writeable. When set,
the enCoRe V M8C stops executing code until a reset event
occurs. This can be either a POR, WDR, or XRES. If an
application wants to stop code execution until a reset, the
preferred method is to use the
HALT
instruction rather than a
register write to this bit.
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,FFh
GIES
WDRS
PORS
Sleep
STOP
# : XX
Legend
#
Access is bit specific. Refer to register detail for additional information.
XX The reset value is 10h after POR/XRES and 20h after a watchdog reset.