ST20-C1 STMICROELECTRONICS [STMicroelectronics], ST20-C1 Datasheet - Page 8

• Manufacturer Part Number: ST20-C1
• Description: Instruction Set Reference Manual
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

2.2 Instruction definitions
For example, the and instruction contains the following description:
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
This section of the instruction definitions lists an y changes to bits of the Status
register which can occur. The Status register is described in more detail in section
3.3.2.
2.1.6
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:
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:
This says that and is a secondar y instruction.
2.2
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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Definition:
Status Register
Comments
“Primary instruction” — indicates one of the 13 functions which may be directly
encoded with an operand in a single byte instruction.
“Secondary instruction” — indicates an instruction which is encoded using opr .
Comments:
Instruction definitions
Areg
Breg
Creg
Secondary instruction.
Breg
Creg
Areg
Areg