SH7713 Datasheet, PDF (140/904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 3 DSP Operating Unit
decrement addressing mode. To perform decrementing, –2 is set in the index register and
addition index register addressing is specified.
When using X/Y data addressing, bit 0 of the address pointer is invalid. Accordingly, bit 0 of the
address pointer and index register must be cleared to 0 in X/Y data addressing.
When accessing X and Y memory using the X and Y buses, the upper word of Ax and Ay is
ignored. The result of Ay+ or Ay+Iy is stored in the lower word of Ay, while the upper word
retains its original value. The Ax and Ax +Ix operations are executed in longword (32 bits) and the
upper word may be changed according to the result.
Single Data Addressing: The following four kinds of addressing can be used with single data
transfer instructions.
• Non-update address register addressing
The As register is an address pointer. An access to @As is performed but As is not updated.
• Increment address register addressing:
The As register is an address pointer. After an access to @As, the As register is incremented
by 2 or 4 (post-increment).
• Addition index register addressing:
The As register is an address pointer. After an access to @As, the value of the Is register is
added to the As register (post-increment).
• Decrement address register addressing:
The As register is an address pointer. Before a data transfer, –2 or –4 is added to the As
register (i.e. 2 or 4 is subtracted) (pre-decrement).
In single data transfer instructions, all bits in 32-bit address are valid.
3.4.3 Modulo Addressing
In double data transfer instructions, a modulo addressing can be used. If the address pointer value
reaches the preset modulo end address while a modulo addressing mode is specified, the address
pointer value becomes the modulo start address.
To control modulo addressing, the modulo register (MOD) extended in the DSP mode and the
DMX and DMY bits of the SR register are used.
The MOD register is provided to set the start and end addresses of the modulo address area. The
upper and lower words of the MOD register store modulo start address (MS) and modulo end
Rev.1.50 Aug. 30, 2006 Page 100 of 860
REJ09B0288-0150