C161RI_1 Datasheet, PDF (309/317 Pages) Siemens Semiconductor Group – 16-Bit CMOS Single-Chip Microcontroller

Instruction Set Summary
C161RI
System Control Instructions
• Resetting the C161RI via software:
• Entering the Idle mode:
• Entering the Power Down mode:
• Servicing the Watchdog Timer:
• Disabling the Watchdog Timer:
• Signifying the end of the initialization routine
(pulls pin RSTOUT high, and disables the effect of
any later execution of a DISWDT instruction):
Miscellaneous
• Null operation which requires 2 bytes of
storage and the minimum time for execution:
• Definition of an unseparable instruction sequence:
• Switch ‘reg’, ‘bitoff’ and ‘bitaddr’ addressing modes
to the Extended SFR space:
• Override the DPP addressing scheme
using a specific data page instead of the DPPs,
and optionally switch to ESFR space:
• Override the DPP addressing scheme
using a specific segment instead of the DPPs,
and optionally switch to ESFR space:
SRST
IDLE
PWRDN
SRVWDT
DISWDT
EINIT
NOP
ATOMIC
EXTR
EXTP
EXTPR
EXTS
EXTSR
Note: The ATOMIC and EXT* instructions provide support for uninterruptable code sequences e.g.
for semaphore operations. They also support data addressing beyond the limits of the
current DPPs (except ATOMIC), which is advantageous for bigger memory models in high
level languages. Refer to chapter “System Programming” for examples.
Protected Instructions
Some instructions of the C161RI which are critical for the functionality of the controller are
implemented as so-called Protected Instructions. These protected instructions use the maximum
instruction format of 32 bits for decoding, while the regular instructions only use a part of it (e.g. the
lower 8 bits) with the other bits providing additional information like involved registers. Decoding all
32 bits of a protected doubleword instruction increases the security in cases of data distortion during
instruction fetching. Critical operations like a software reset are therefore only executed if the
complete instruction is decoded without an error. This enhances the safety and reliability of a
microcontroller system.
Semiconductor Group
22-4
1998-05-01