Zilog Z8F0130 - Manual (Page 151)

eZ8
™
CPU Core
User Manual
UM012820-0810 DEC Instruction
136
Attributes
1
Escaped Mode Addressing
Using Escaped Mode Addressing, address modes R or IR can specify a
working register. If the destination address is prefixed by
Eh ( 1110b ), a
working register is inferred. For example, if Working Register R12 ( Ch ) is
the preferred destination operand, use ECh as the destination operand in
the Op Code. To access registers with addresses E0h to EFh , either set the
Working Group Pointer, RP[7:4] , to Eh or use indirect addressing.
Sample Usage
If Working Register R10 contains 2Ah , the following statement leaves the
value 29h in Working Register R10 and clears the Z, V, and S flags:
DEC R10

Object Code: 30 EA
If Register B3h contains CBh , and Register CBh contains 01h , the follow-
ing statement leaves the value 00h in Register CBh , sets the Z flag, and
clears the V and S flags:
DEC @B3h

Object Code: 31 B3
1. The location of the DEC R1 instruction has been moved from its former Z8 CPU Op Code lo-
cation at 00h. The location of the DEC IR1 instruction has been moved from its former Z8 CPU Op
Code location at 01h.
Mnemonic Destination
Op
Code
(Hex)
Operand 1 Operand 2 Operand 3
DEC R1 30 R1 — —
DEC @R1 31 R1 — —