beautypg.com

Micro stack (mstack), Figure 5–3. a pop operation, 3 micro stack (mstack) – Texas Instruments TMS320C2XX User Manual

Page 105

background image

Program-Address Generation

5-6

Figure 5–3. A Pop Operation

Before Instruction

After Instruction

Accumulator

Accumulator

or memory

82h

or memory

45h

location

location

45h

16h

16h

7h

Stack

7h

Stack

33h

33h

42h

42h

56h

56h

37h

37h

61h

61h

61h

5.1.3

Micro Stack (MSTACK)

The program-address generation logic uses the 16-bit-wide, 1-level-deep
MSTACK to store a return address before executing certain instructions.
These instructions use the program-address generation logic to provide a se-
cond address in a two-operand instruction. These instructions are: BLDD,
BLPD, MAC, MACD, TBLR, and TBLW. When repeated, these instructions
use the PC to increment the first operand address and can use the auxiliary
register arithmetic unit (ARAU) to generate the second operand address.
When these instructions are used, the return address (the address of the next
instruction to be fetched) is pushed onto the MSTACK. Upon completion of the
repeated instruction, the MSTACK value is popped back into the program-ad-
dress generation logic. The MSTACK operations are not visible to you. Unlike
the stack, the MSTACK can be used only by the program-address generation
logic; there are no instructions that allow you to use the MSTACK for storage.