NEC PD750008 - Manual (Page 257)

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CHAPTER 11 INSTRUCTION SET
CHAPTER 11 INSTRUCTION SET
The instruction set of the µPD750008 is an improved and extended version of the 75X series instruction
set. This instruction set takes over the instruction set of the 75X series, having the following features:
(1) Bit manipulation instructions allowing a wide variety of applications
(2) Efficient 4-bit manipulation instructions
(3) Eight-bit instructions comparable to 8-bit microcomputers
(4) GETI instruction for reducing program sizes
(5) String-effect instructions and number system conversion instructions for increased program efficiency
(6) Table reference instructions suitable for successive references
(7) 1-byte relative branch instructions
(8) NEC standard mnemonics designed for clarity and readability
See Section 3.2 for the addressing modes applicable to data memory manipulation and register banks used
for instruction execution.
11.1 UNIQUE INSTRUCTIONS
This section outlines the unique instructions among the µPD750008 instruction set.
11.1.1 GETI Instruction
The GETI instruction converts any of the following instructions to a 1-byte instruction:
(a) Subroutine call instruction for the entire space
(b) Branch instruction for the entire space
(c) Arbitrary 2-byte instruction operating with two machine cycles (Except the BRCB and CALLF
instructions)
(d) A combination of two 1-byte instructions
The GETI instruction references the table located at addresses 0020H to 007FH in program memory, and
executes referenced 2-byte data as an instruction of (a), (b), (c), or (d) above. This means that 48 instructions
consisting of (a) to (d) can be converted to 1-byte instructions.
Thus the GETI instruction can be used to convert frequently used instructions of (a) to (d) to 1-byte
instructions to reduce the number of program bytes significantly.
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