IP2022 User’s Manual—Instruction Set Architecture www.ubicom.com 97 3.7 Self-Programming Instructions The IP2022 has several instructions used to read and write the
program RAM and the program flash memory. These instructions
allow the program flash memory to be read and written through
special-purpose registers in the data memory space, which allows
the flash memory to be used to store both program code and data. Because no special programming voltage is required to write to
the  flash  memory,  any  application  may  take  advantage  of  this
feature at run-time. Typical uses include saving phone numbers
and   passwords,   downloading   new   or   updated   software,   and
logging  infrequent  events  such  as  errors  and  Watchdog  Timer
resets. The self-programming instructions are not affected by the code-
protection flag (the CP bit of the FUSE1 register), so the entire
program memory is visible to any software running on the IP2022. There are five instructions used for self-programming, as shown in
Table 3-9. Certain uses of the instructions are not valid. In these
cases,  the  instruction  is  executed  as  though  it  were  a  nop
instruction (i.e. the program counter is incremented, but no other
registers or bits are affected).