NEC PD754144 User Manual
Page 291
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.