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Pipeline Registers

The OPGDBR is available for read operations only through the JTAG/OnCE serial interface and only when the chip is in debug mode. Any attempted read of the OPGDBR when the chip is not in debug mode results in the JTAG shifter capturing and shifting unspecified data.

NOTE:

The OPGDBR accesses corrupt PDB. Therefore, if the user needs to save the value on PDB, an OPDBR read should be executed before the first OPGDBR access in any debug session.

12.6.7 OnCE FIFO History Buffer

To aid debugging activity and keep track of the program flow, a read-only FIFO buffer is provided. The FIFO stores PAB values from the instruction flow. The FIFO consists of fetch, decode, and execute registers as well as an optional (peripheral) change-of-flow FIFO. Figure 12-10 illustrates a block diagram of the OnCE FIFO History Buffer.

 

OnCE™ Module

12-27

OnCE™ Module

16

PAB

DSP Core Fetch Address

(OPABFR)

DSP Core Decode Address

(OPABDR)

DSP Core Execute Address

(OPABER)

16

Circuitry On-Core

Circuitry Off-Core

FIFO Location 1

FIFO Location 2

FIFO Location 3

FIFO Location 4

FIFO Location 5

FIFO Location 6

FIFO Location 7

FIFO Location 8

16

FIFO Shift Register

(OPFIFO)

Read/Write via OnCE

Read/Write via OnCE

Read/Write via OnCE

Read/Write

via OnCE

AA1393

Figure 12-10. OnCE FIFO History Buffer

12-28

DSP56824 User’s Manual

 

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