Texas Instruments TMS320C67X/C67X+ DSP Addressing Mode Register AMR, Bit Field Value Description

Control Register File

2.7.3Addressing Mode Register (AMR)

For each of the eight registers (A4–A7, B4–B7) that can perform linear or circu- lar addressing, the addressing mode register (AMR) specifies the addressing mode. A 2-bit field for each register selects the address modification mode: linear (the default) or circular mode. With circular addressing, the field also specifies which BK (block size) field to use for a circular buffer. In addition, the buffer must be aligned on a byte boundary equal to the block size. The mode select fields and block size fields are shown in Figure 2−3 and described in Table 2−5.

Figure 2−3. Addressing Mode Register (AMR)

31					26	25				21	20				16
		Reserved						BK1					BK0
			R-0					R/W-0					R/W-0
15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0

B7 MODE B6 MODE

B5 MODE B4 MODE A7 MODE A6 MODE A5 MODE

A4 MODE

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Legend: R = Readable by the MVC instruction; W = Writeable by the MVC instruction; -n= value after reset

Table 2−5. Addressing Mode Register (AMR) Field Descriptions

Bit	Field	Value	Description
31−26	Reserved	0	Reserved. The reserved bit location is always read as 0. A value written to
			this field has no effect.
25−21	BK1	0−1Fh	Block size field 1. A 5-bit value used in calculating block sizes for circular
			addressing. Table 2−6 shows block size calculations for all 32 possibilities.
			Block size (in bytes) = 2(N+1), where N is the 5-bit value in BK1
20−16	BK0	0−1Fh	Block size field 0. A 5-bit value used in calculating block sizes for circular
			addressing. Table 2−6 shows block size calculations for all 32 possibilities.
			Block size (in bytes) = 2(N+1), where N is the 5-bit value in BK0
15−14	B7 MODE	0−3h	Address mode selection for register file B7.
		0	Linear modification (default at reset)
		1h	Circular addressing using the BK0 field
		2h	Circular addressing using the BK1 field
		3h	Reserved

2-10 CPU Data Paths and Control SPRU733