Address Generation Unit

 

 

 

XABA

XABB

PAB

 

 

 

32

32

32

R8/B0

M0

N0

 

R0

 

R9/B1

M1

N1

Address

R1

 

R10/B2

M2

N2

R2

 

Arithmetic

 

R11/B3

M3

N3

R3

 

Unit (AAU)

 

R12/B4

MCTL

 

 

R4

 

R13/B5

 

 

R5

 

 

 

 

 

R14/B6

 

 

 

R6

 

R15/B7

 

 

 

R7

 

 

 

 

 

NSP

 

 

 

 

 

ESP

 

 

 

 

Bit

 

 

 

Program Counter (PC) Address

Mask

 

 

 

 

 

Unit

 

 

 

 

 

(BMU)

 

 

 

Memory Data Bus 1 (XDBA)

64

 

 

 

Memory Data Bus 2 (XDBB)

64

 

 

Figure 2-12. AGU Block Diagram

All sixteen address registers (R0–R15) as well as the NSP or ESP are used for generating addresses in the register indirect addressing modes. All four offset registers (N0–N3) can be used by all sixteen address registers. The four modifier registers (M0–M3) can only be used by the low bank of eight address registers (R0–R7).

The base address (Bn) registers are uniquely associated with the low bank of Rn registers such that B0 is used with R0, B1 with R1, and so on.

The BMU is used to perform bit mask operations such as setting, clearing, changing, or testing bits in a destination according to an immediate mask operand. Data is loaded into the BMU over the data memory buses XDBA or XDBB. The result is written back over XDBA or XDBB to the destinations in the next cycle. All bit mask instructions are typically executed in two cycles and work on 16-bit data. This data can be a memory location or a portion (high or low) of a register. For more information, see Section 2.3.6, “Bit Mask Instructions.”

2-32

SC140 DSP Core Reference Manual

Page 64
Image 64
Freescale Semiconductor SC140 specifications Address, Arithmetic, Unit AAU