ST20-C1 datasheet(8/205 Pages) STMICROELECTRONICS

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2.2 Instruction definitions

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For example, the

and instruction contains the following description:

Definition:

Areg

′← Breg ∧ Areg

Breg

′← Creg

Creg

′← Areg

This says that the integer stack is rotated and Areg is assigned the bitwise AND of the

values that were initially in Breg and Areg. After the instruction has executed Breg

contains the value that was originally in Creg, and Creg has the value that was in

Areg.

The notation is described more fully in section 2.2.

2.1.5

Status Register

This section of the instruction definitions lists an y changes to bits of the Status

3.3.2.

2.1.6

Comments

This section is used for listing other information about the instructions that may be of

interest. This includes an indication of the type of the instruction:

“Primary instruction” — indicates one of the 13 functions which may be directly

encoded with an operand in a single byte instruction.

“Secondar y instruction” — indicates an instruction which is encoded using

opr.

An explanation of the primary and secondary instruction formats is given in section

3.4.

The Comments section also describes any situations where the operation of the

instruction is undefined or invalid and any limits to the parameter values.

For example, the only comment listed for the

and instruction is:

Comments:

Secondary instruction.

This says that

and is a secondar y instruction.

2.2

Instruction definitions

The following sections give a full description of the notation used in the formal defini-

tion section of the instruction descriptions.

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