source: buchla-68k/orig/doc/Thunder/C25ADR.TXT@ d21fc6f

TMS320C25 Direct Addressing Mode
--------------------------------

Instruction bits
Op-Code  Address
-------- --------
xxxxxxxx 0AAAAAAA       Direct memory address -- AAAAAAA is the address 0..7F

                        The address is formed from the Data Page register
                        and the address bits of the instruction.

                        The data page register points to one of 512 pages of
                        128 words each.  The address bits point to the word
                        in the page.

TMS320C25 Indirect Addressing Mode
----------------------------------

Instruction bits
Op-Code  Address
-------- --------
xxxxxxxx 1RIDNYYY       Indirect addressing -- address is in AR(ARP)
          ||||-+-
          |||| |
          |||| +------- next ARP value if N = 1
          |||+--------- 0 = leave ARP unchanged,  1 = set ARP = YYY
          ||+---------- 0 = no change,  1 = decrement AR(ARP) by 1 or AR0
          |+----------- 0 = no change,  1 = increment AR(ARP) by 1 or AR0
          +------------ 0 = use 1 as the value,  1 = use AR0 as the value

                        The address is contained in the Auxilliary register
                        pointed to by ARP.  This register may be modified
                        and a new one selected by the appropriate choice of
                        address modes shown in the table below:

Instruction bits
Op-Code  Address        Notation        Operation
-------- --------       --------        -------------------------------------
xxxxxxxx 10000YYY       *               No change to ARs/ARP
xxxxxxxx 10001YYY       *,Y             Y -> ARP
xxxxxxxx 10010YYY       *-              AR(ARP) - 1 -> AR(ARP)
xxxxxxxx 10011YYY       *-,Y            AR(ARP) - 1 -> AR(ARP);  Y -> ARP
xxxxxxxx 10100YYY       *+              AR(ARP) + 1 -> AR(ARP)
xxxxxxxx 10101YYY       *+,Y            AR(ARP) - 1 -> AR(ARP);  Y -> ARP
xxxxxxxx 11000YYY       *BR0-           AR(ARP) - rcAR0 -> AR(ARP)
xxxxxxxx 11001YYY       *BR0-,Y         AR(ARP) - rcAR0 -> AR(ARP);  Y -> ARP
xxxxxxxx 11010YYY       *0-             AR(ARP) - AR0 -> AR(ARP)
xxxxxxxx 11011YYY       *0-,Y           AR(ARP) - AR0 -> AR(ARP);  Y -> ARP
xxxxxxxx 11100YYY       *0+             AR(ARP) + AR0 -> AR(ARP)
xxxxxxxx 11101YYY       *0+,Y           AR(ARP) + AR0 -> AR(ARP);  Y -> ARP
xxxxxxxx 11110YYY       *BR0+           AR(ARP) + rcAR0 -> AR(ARP)
xxxxxxxx 11111YYY       *BR0+,Y         AR(ARP) + rcAR0 -> AR(ARP);  Y -> ARP