Zilog Z8F0130 Manual do Utilizador descarregar pdf (Página 151)

eZ8

™

CPU Core

User Manual

UM012820-0810 DEC Instruction

136

Attributes

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

Code

(Hex) Operand 1 Operand 2 Operand 3

DEC R1 30 R1 — —

DEC @R1 31 R1 — —

1 2 ... 146 147 148 149 150 151 152 153 154 155 156 ... 313 314

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