TMS320F datasheet(88/389 Pages) TI

88 / 389 page

Direct Addressing Mode

6-4

6.2

Direct Addressing Mode

In the direct addressing mode, data memory is addressed in blocks of 128

words called data pages. The entire 64K of data memory consists of 512 data

pages labeled 0 through 511, as shown in Figure 6–3. The current data page

is determined by the value in the 9-bit data page pointer (DP) in status register

ST0. For example, if the DP value is 0 0000 00002, the current data page is

0. If the DP value is 0 0000 00102, the current data page is 2.

Figure 6–3. Pages of Data Memory

1111 1111 1

0000 0000 1

0000 0001 0

0000 0000 0

Data Memory

Page 0: 0000h–007Fh

Page 1: 0080h–00FFh

Page 2: 0100h–017Fh

Page 511: FF80h–FFFFh

000 0000

Offset

DP Value

0000 0000 0

111 1111

0000 0000 1

1111 1111 1

000 0000

111 1111

000 0000

111 1111

000 0000

111 1111

In addition to the data page, the processor must know the particular word being

referenced on that page. This is determined by a 7-bit offset (see Figure 6–3).

The offset is supplied by the seven least significant bits (LSBs) of the IR regis-

ter shown in Figure 6–4,

Instruction Register (IR) Contents in Direct Address-

ing Mode instruction register, on page 6-5, which holds the opcode for the

next instruction to be executed. In direct addressing mode, the contents of the

instruction register has the format.

TMS320F Datasheet(PDF) 88 Page - Texas Instruments