UPD75237 Datasheet, PDF (150/191 Pages) NEC – 4-BIT SINGLE-CHIP MICROCOMPUTER

µPD75237
8. INSTRUCTION SET
8.1 CHARACTERISTIC INSTRUCTIONS OF µPD75237
(1) GETI instruction
The GETI instruction is a 1-byte instruction to execute the following three types of operations by referring
to the 2-byte table in the program memory.
It can considerably help to decrease the number of program steps.
(a) Subroutine call to 16K-byte space (0000H to 3FFFH) of table data as call instruction call address.
(b) Branch to 16K-byte space (0000H to 3FFFH) of table data as branch instruction branch address
(c) Execution of table data as 2-byte instruction (except BRCB and CALLF instructions)
(d) Execution of table data as 1-byte instruction and 2 operation codes.
As shown in Fig. 3-2, the table addressed referred to by GETI instruction as 0020H to 007FH of the program
memory and data can be set in 48 tables.
When describing table addresses as operands, describe even addresses.
Note
1. 2-byte instructions which can be referred to by GETI instruction are limited to 2-machine cycle
instructions.
2. When referring to two 1-byte instructions by GETI instruction, combinations are limited as follows.
1st Byte Instruction
MOV A, @HL
MOV @HL, A
XCH A, @HL
MOV A, @DE
XCH A, @DE
MOV A, @DL
XCH A, @DL
2nd Byte Instruction
INCS
L
DECS
L
INCS
H
DECS
H
INCS
HL
INCS
E
DECS
E
INCS
D
DECS
D
INCS
DE
INCS
L
DECS
L
INCS
D
DECS
D
3. When a branch instruction or subroutine instruction is referenced by a GETI instruction, the relevant
branch destination or subroutine call address must be within 16K bytes (0000H to 3FFFH). It is not
possible to use a GETI instruction to reference a branch instruction or subroutine call instruction to an
address outside this range (4000H to 5F7FH).
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