MAS281 datasheet(18/55 Pages) DYNEX

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MAS281

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Figure 9: Register Set Model

Figure 10: Data Formats

4.2.4 IMMEDIATE LONG (IM, IMX)

There are two formats which implement Immediate Long

Addressing; one allows indexing and one does not. For the

indexable form, if the specified index register, RX, is not equal

to zero, the contents of RX are added to the immediate field to

form the required operand; otherwise, the immediate field

contains the required operand.

4.2.5 IMMEDIATE SHORT (IS)

In this mode the required 4-bit operand is contained within

the 16-bit instruction. The Immediate Short addressing mode

accommodates two formats; one which interprets the contents

of the immediate field as positive data and the other which

interprets the contents of the immediate field as a negative

data.

4.2.5.1 IMMEDIATE SHORT POSITIVE (ISP)

The immediate operand is treated as a positive integer

between 1 and 16.

4.2.5.2 IMMEDIATE SHORT NEGATIVE (ISN)

The immediate operand is treated as a negative integer

between -1 and -16. Its internal form is a two’s complement,

sign-extended 16-bit number.

4.2.6 INSTRUCTION COUNTER RELATIVE (ICR)

This addressing mode is used for 16-bit branch

instructions. The contents of the instruction counter minus two

(the address of the current instruction) is added to the sign-

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