Document # 001-20559 Rev. *D
315
System Resets
30.3.2
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 PSoC device.
Bit 7: GIES.
The Global Interrupt Enable Status bit is a
read only status bit and its use is discouraged. The GIES bit
is a legacy bit which was used to provide the ability to read
the GIE bit of the CPU_F register. However, the CPU_F reg-
ister 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.
The WatchDog Reset Status 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 zero to its bit position in the CPU_SCR0 register.
Bit 4: PORS.
The Power On Reset Status (PORS) bit,
which is the watchdog enable bit, is set automatically by a
POR or External Reset (XRES). If the bit is cleared by user
code, the watchdog timer is enabled. Once 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.
The Sleep 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.
There are two special features of this register bit that
ensures 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). Sec-
ond, there is a hardware interlock to ensure that, once set,
the Sleep bit may not be cleared by an incoming interrupt
until the sleep circuit has finished performing the sleep
sequence and the system-wide power down signal has been
asserted. This prevents the sleep circuit from being inter-
rupted in the middle of the process of system power down,
possibly leaving the system in an indeterminate state.
Bit 0: STOP.
The STOP bit is readable and writeable.
When set, the PSoC M8C stops executing code until a reset
event occurs. This can be either a POR or 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
0,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 and 20h after a watchdog reset.
Содержание PSoC CY8C23533
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