ST72324BJ2 datasheet(133/188 Pages) STMICROELECTRONICS

Part #	ST72324BJ2

Description	8-bit MCU, 3.8 to 5.5 V operating range with 8 to 32 Kbyte Flash/ROM, 10-bit ADC, 4 timers, SPI, SCI

PDF	188 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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133 / 188 page

ST72324B

Instruction set

133/188

Using a prebyte

The instructions are described with one to four opcodes.

In order to extend the number of available opcodes for an 8-bit CPU (256 opcodes), three

different prebyte opcodes are defined. These prebytes modify the meaning of the instruction

they precede.

The whole instruction becomes:

PC-2

End of previous instruction

PC-1

Prebyte

Opcode

PC+1

Additional word (0 to 2) according to the number of bytes required to compute the

effective address

These prebytes enable the instruction in Y as well as indirect addressing modes to be

implemented. They precede the opcode of the instruction in X or the instruction using direct

addressing mode. The prebytes are:

PDY 90

Replace an X based instruction using immediate, direct, indexed, or inherent

addressing mode by a Y one.

PIX 92

Replace an instruction using direct, direct bit, or direct relative addressing mode

to an instruction using the corresponding indirect addressing mode.

It also changes an instruction using X indexed addressing mode to an instruction

using indirect X indexed addressing mode.

PIY 91

Replace an instruction using X indirect indexed addressing mode by a Y one.

ST72324BJ2 Datasheet(PDF) 133 Page - STMicroelectronics