SH7721 datasheet(145/1524 Pages) RENESAS

145 / 1524 page

Section 3 DSP Operating Unit

Rev. 3.00 Jan. 18, 2008 Page 83 of 1458

REJ09B0033-0300

3.2

DSP Mode Resources

3.2.1

Processing Modes

The CPU processing modes can be extended using the mode bit (MD) and DSP bit (DSP) in the

status register (SR), as shown below.

Table 3.1

CPU Processing Modes

Description

DSP

Processing Mode

Access of Resources

Protected in Privileged Mode

or Privileged Instruction

Execution

DSP Extended

Functions

User mode

Prohibited

Invalid

User DSP mode

Prohibited

Valid

Privileged mode

Allowed

Invalid

Privileged DSP mode Allowed

Valid

As shown above, the extension of the DSP function by the DSP bit can be specified independently

of the control by the MD bit. Note, however, that the DSP bit can be modified only in privileged

mode. Before the DSP bit is modified, a transition to privileged mode or privileged DSP mode is

necessary.

3.2.2

DSP Mode Memory Map

In DSP mode, a part of the P2 area in the virtual address space can be accessed in user DSP mode.

When this area is accessed in user DSP mode, this area is referred to as a Uxy area. X/Y memory

is then assigned to this Uxy area. Accordingly, X/Y memory can also be accessed in user DSP

mode.

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