IP2022 User’s Manual—System Architecture www.ubicom.com 29 within  the  same  page.  Longer  jumps  and  calls  require  using  a page instruction to load the upper address bits into the PA2:0 bits of the STATUS register. The page instruction must immediately
precede the jump or call instruction. The PA2:0 bits should not be
modified by writing directly to the STATUS register, because this
may cause  a mismatch  between the PA2:0 bits in the STATUS
register and the current program counter (see Section 2.3.2). For
more information about program flash memory, see Section 3.7. External  memory  is  not  shown in  Figure  2-3  because  the  CPU
cannot execute instructions directly out of external memory. For
more information about external memory, see Section 4.11. 2.3.1 Loading the Program RAM Software  loads  the  program  RAM  from  program  flash  memory
using the iread/ireadi and iwrite/iwritei instructions.
The  iread  instruction  reads  the  16-bit  word  specified  by  the
address held in the ADDRX/ADDRH/ADDRL register. This word
can  be  in  program  flash  memory,  program  RAM,  or  external
memory. When the iread instruction is executed, bits 15:8 of the
word are loaded into the DATAH register, and bits 7:0 are loaded
into  the  DATAL  register.  The  address  is  a  word-aligned  byte
address  (i.e.  an  address  that  is  zero  in  its  LSB).  The  ireadi
instruction is identical to the iread instruction, except that it also
increments the address by 2. The   iwrite   instruction   writes   the   16-bit   word   held   in   the
DATAH/DATAL registers to the program RAM location specified by