IP2022 Data Sheet www.ubicom.com 33 4.1.2 Direct Addressing Mode Figure  4-1  shows  the  direct  addressing  mode  used  to
reference the special-purpose registers. Seven bits from
the “fr” field allow addressing up to 128 special-purpose
registers.   (Not   all   128   locations   in   this   space   are
implemented    in    the    IP2022;    several    locations    are
reserved for future expansion.) Figure 4-1  Direct Mode, Special-Purpose Registers The following code example uses direct mode. Figure  4-2  shows  the  direct  addressing  mode  used  to
reference the global registers. This mode is distinguished
from   the   mode   used   to   access   the   special-purpose
registers with bit 7 of the “fr” field. Because these registers
have this additional addressing mode not available for the
other data memory locations, they are especially useful
for holding global variables and frequently accessed data. Figure 4-2  Direct Mode, Global Registers Note:   Addresses   from   0x000   to   0x01F   can   only   be
accessed with Direct mode. 4.1.3 Indirect Addressing Mode The indirect addressing mode is used when all of the bits
in the “fr” field are clear. The location of the operand is
specified by a 12-bit pointer in the IPH and IPL registers.
The upper four bits of the IPH register are not used. Figure
4-3 shows indirect mode. Figure 4-3  Indirect Mode The following code example uses indirect mode. mov w,0x0012   ;load W with the contents of ;the memory location at 0x0012
;(the DATAL register) 515-007a.eps               127
Special-Purpose Registers 7 0   9-Bit "fr" Field
from Instruction 0 8 0  n  n  n  n  n  n  n 0 7 6 515-008a.eps               127
Global Registers 7 0   9-Bit "fr" Field
from Instruction 0 8 1  n  n  n  n  n  n  n 0 7 6 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 515-009a.eps               127
Special-Purpose Registers   3840 Bytes
Data Memory IPH Register IPL 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 0 8 0 0 0 0 0 0 0 0 0               128
Global Registers