
DocID13284 Rev 2
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UM0404
The central processing unit (CPU)
Beside its normal operation there are the following particular CPU states:
•
RESET state:
Any reset (hardware, software, watchdog) forces the CPU into a pre-
defined active state.
•
IDLE state:
The clock signal to the CPU itself is switched off, while the clocks for the
on-chip peripherals keep running.
•
POWER DOWN state:
All of the on-chip clocks are switched off.
A transition into an active CPU state is forced by an interrupt (if being IDLE) or by a reset (if
being in POWER DOWN mode).
The IDLE, POWER DOWN and RESET states can be entered by particular ST10F276
system control instructions. A set of Special Function Registers is dedicated to the functions
of the CPU core:
•
General System Configuration:
SYSCON (RP0H)
•
CPU Status Indication and Control:
PSW
•
Code Access Control:
IP, CSP
•
Data Paging Control:
DPP0, DPP1, DPP2, DPP3
•
GPRs Access Control:
CP
•
System Stack Access Control:
SP, STKUN, STKOV
•
Multiply and Divide Support:
MDL, MDH, MDC
•
ALU Constants Support:
ZEROS, ONES