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NEC PD754144 User Manual

Page 291

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CHAPTER 11 INSTRUCTION SET

291

User’s Manual U10676EJ3V0UM

References the 2-byte data at the program memory address specified by (taddr), (taddr+1) and executes it as an

instruction.

The area of the reference table consists of addresses 0020H to 007FH. Data must be written to this area in advance.

Write the mnemonic of a 1-byte or 2-byte instruction as the data as is.

When a 3-byte call instruction and 3-byte branch instruction is used, data is written by using an assembler directive

(TCALL or TBR).

Only an even address can be specified by taddr.

Caution

Only a 2-machine-cycle instruction can be set to the reference table as a 2-byte instruction (except the BRCB and

CALLF instructions). Two 1-byte instructions can be set only in the following combinations.

Instruction of 1st Byte

Instruction of 2nd Byte

MOV

A, @HL

INCS

L

MOV

@HL, A

DECS

L

XCH

A, @HL

INCS

H

DECS

H

INCS

HL

MOV

A, @DE

INCS

E

XCH

A, @DE

DECS

E

INCS

D

DECS

D

INCS

DE

MOV

A, @DL

INCS

L

XCH

A, @DL

DECS

L

INCS

D

DECS

D

The contents of the PC are not incremented while the GETI instruction is executed. Therefore, after the reference

instruction has been executed, processing continues from the address next to that of the GETI instruction.

If the instruction preceding the GETI instruction has a skip function, the GETI instruction is skipped in the same

manner as the other 1-byte instructions. If the instruction referenced by the GETI instruction has a skip function, the

instruction that follows the GETI instruction is skipped.

If an instruction having a string effect is referenced by the GETI instruction, it is executed as follows.

If the instruction preceding the GETI instruction has the string effect of the same group as the referenced

instruction, the string effect is lost and the referenced instruction is not skipped when GETI is executed.

If the instruction next to GETI has the string effect of the same group as the referenced instruction, the string

effect by the referenced instruction is valid, and the instruction following that instruction is skipped.

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