IP2022 Data Sheet www.ubicom.com 37 The following code example uses indirect mode. 4.1.4 Indirect-with-Offset Modes The indirect-with-offset addressing mode is used when bit
8  of  the  “fr”  field  is  set.  The  location  of  the  operand  is
specified by a 7-bit unsigned immediate from the “fr” field
added  to  a  12-bit  base  address  in  a  pointer  register.
Addresses  from  0x000  to  0x01F  cannot  be  accessed
reliably with this addressing mode, therefore it must not
be used for this purpose. (Direct mode should be used
instead.) When bit 7 of the “fr” field is clear, the DPH/DPL register
is   selected   as   the   pointer   register.   This   register   is
accessed  using  the  loadh  and  loadl  instructions,
which load its high and low bytes, respectively. The upper
four  bits  of  the  DPH  register  are  not  used.  Figure  4-5
shows indirect-with-offset addressing using the DPH/DPL
register as the pointer register. Figure 4-5  Indirect-with-Offset Mode, Data Pointer The   following   code   example   uses   indirect-with-offset
mode. When bit 7 of the “fr” field is set, the SPH/SPL register is
selected as the pointer register. The upper four bits of the
SPH register are not used. Figure 4-6 shows indirect-with-
offset mode using the SPH/SPL register. In addition to this
indirect-with-offset   addressing   mode,   there   are   also push    and    pop    instructions    which    automatically increment  and  decrement  the  SPH/SPL  register  while
performing a data transfer between the top of stack and a
data  memory  location  specified  by  the  “fr”  field.  Stacks
grow  down  from  higher  addresses  to  lower  addresses. mov w,#0x03 ;load W with 0x03 mov iph,w ;load the high byte of the ;indirect pointer from W mov w,#0x85 ;load W with 0x85 mov ipl,w ;load the low byte of the
;indirect pointer from W mov w,(ip) ;load W with the contents of
;the memory location at
;effective address 0x0385 MyStuff= 0x038D ;define address MyStuff loadh MyStuff    ;load the high byte of the ;DPH/DPL pointer register
;with 0x03 loadl MyStuff    ;load the low byte of the ;DPH/DPL pointer register
;with 0x8D mov w,8(dp)    ;load W with the contents of ;the memory location at
;effective address 0x038D
;(i.e. 0x0385 + 0x0008) 515-026.eps            128
Special-Purpose Registers DPH Register DPL Register 7 0 n 0 n 7 n n n n n n n X 3 4 7 X X X n n n 0   9-Bit "fr" Field
from Instruction 1 8 0 mmmmmmm 0 + 7 6   3840 Bytes
Data Memory            128
Global Registers