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Zilog Z8F0130 User Manual

Page 251

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eZ8

CPU Core

User Manual

UM012820-0810

SUBX Instruction

236

Attributes

Escaped Mode Addressing

Using Escaped Mode Addressing, address mode ER for the source or des-
tination specifies a working register with 4-bit addressing.

If the high byte of the source or destination address is

EEh

(

11101110b

),

a working register is inferred. For example, the operand

EE3h

selects

Working Register R3. The full 12-bit address is provided by

{RP[3:0],

RP[7:4], 3h}

.

To access registers on Page

Eh

(addresses

E00h

to

EFFh

), set the Page

Pointer, RP[3:0], to

Eh

and set the Working Group Pointer,

RP[7:4]

, to

the preferred Working Group.

Sample Usage

If Register

234h

contains the value

2Eh

, and Register

912h

contains the

value

1Bh

, the following statement leaves the value

13h

in Register

234h

, sets the D flag, and clears the C, Z, S, V, and H flags:

SUBX 234h, 912h

Object Code: 28 91 22 34

If Register

56Ch

contains the value

2Ah

, the following statement leaves

the value

27h

in Register

56Ch

, sets the D flag, and clears the C, Z, S, V,

and H flags:

SUBX 56Ch, #03h

Object Code: 29 03 05 6C

Mnemonic

Destination,
Source

Op
Code
(Hex)

Operand 1 Operand 2 Operand 3

SUBX

ER1, ER2

28

ER2[11:4]

{ER2[3:0],
ER1[11:8]}

ER1[7:0]

SUBX

ER1, IM

29

IM

{0h,
ER1[11:8]}

ER1[7:0]