Zilog Z8F0130 Manual do Utilizador descarregar pdf (Página 148)

eZ8

™

CPU Core

User Manual

UM012820-0810 DA Instruction

133

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 addition is performed using the BCD value 15 and 27, the result should

be 42. The sum is incorrect, however, when the binary representations are

added in the destination location using standard binary arithmetic.

If the result of the addition is stored in Register 5Fh, the following state-

ment adjusts this result to obtain the correct BCD representation.

5Fh

Object C?de: 40 5F

Mnemonic Destination

Code

(Hex) Operand 1 Operand 2 Operand 3

DA R1 40 R1 — —

DA @R1 41 R1 — —

0001 0101 = 15h

0010 0111 = 27h

0011 1100 = 3Ch

1 2 ... 143 144 145 146 147 148 149 150 151 152 153 ... 313 314

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Zilog Z8F0130 Manual do Utilizador Página 148