NEC PD754144 - Manual (Page 234)

234 User’s Manual U10676EJ3V0UM
CHAPTER 11 INSTRUCTION SET
The instruction set of the
µPD754244 is based on the instruction set of the 75X Series and therefore maintains
compatibility with the 75X Series, but with the following improved features.
(1) Bit manipulation instructions for various applications
(2) Efficient 4-bit manipulation instructions
(3) 8-bit manipulation instructions comparable to those of 8-bit microcontrollers
(4) GETI instruction reducing program size
(5) String-effect and base number adjustment instructions enhancing program efficiency
(6) Table reference instructions ideal for successive reference
(7) 1-byte relative branch instruction
(8) Easy-to-understand, well-organized NEC standard mnemonics
For the addressing modes applicable to data memory manipulation and the register banks valid for instruction
execution, refer to 3.2 Bank Configuration of General-Purpose Registers.
11.1 Unique Instructions
This section describes the instructions unique to the
µPD754244’s instruction set.
11.1.1 GETI instruction
The GETI instruction converts the following instructions into 1-byte instructions.
(a) Subroutine call instruction to 4 KB space (0000H to 0FFFH)
(b) Branch instruction to 4 KB space (0000H to 0FFFH)
(c) Any 2-byte, 2-machine-cycle instruction (except BRCB and CALLF instructions)
(c) Combination of two 1-byte instructions
The GETI instruction references a table at addresses 0020H to 007FH of the program memory and executes the
referenced 2-byte data as an instruction of (a) to (d). Therefore, 48 types of instructions can be converted into 1-
byte instructions.
If instructions that are frequently used are converted into 1-byte instructions by using this GETI instruction, the
number of bytes of the program can be substantially decreased.