Motorola MCF5282, MCF5281 user manual Command Sequence Diagrams

Models: MCF5282 MCF5281

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Background Debug Mode (BDM)

29.5.3.2 Command Sequence Diagrams

The command sequence diagram in Figure 29-16shows serial bus traffic for commands. Each bubble represents a 17-bit bus transfer. The top half of each bubble indicates the data the development system sends to the debug module; the bottom half indicates the debug module’s response to the previous development system commands. Command and result transactions overlap to minimize latency.

Commands transmitted to the debug module

Command code transmitted during this cycle

 

High-order 16 bits of memory address

 

 

 

 

Low-order 16 bits of memory address

 

 

 

 

Non-serial-related

Sequence taken if operation

 

 

 

activity

 

 

 

 

has not completed

 

 

 

 

READ

 

Next

READ (LONG)

MS ADDR

LS ADDR

XXX

Command

MEMORY

???

’NOT READY’

’NOT READY’

’NOT READY’

Code

LOCATION

 

 

 

 

 

 

XXX

NEXT CMD

 

XXX

NEXT CMD

 

’ILLEGAL’

’NOT READY’

 

MS RESULT

LS RESULT

 

 

Data used from this transfer

XXX

NEXT CMD

 

 

 

 

BERR

’NOT READY’

 

 

 

 

Sequence taken if illegal command

 

 

 

 

 

 

 

 

is received by debug module

 

 

Sequence taken if bus error

 

 

Results from previous command

 

 

 

 

 

 

occurs on memory access

 

 

 

 

 

 

Responses from the debug module

 

 

 

High- and low-order 16 bits of result

 

 

 

Figure 29-16. Command Sequence Diagram

The sequence is as follows:

In cycle 1, the development system command is issued (READ in this example). The debug module responds with either the low-order results of the previous command or a command complete status of the previous command, if no results are required.

In cycle 2, the development system supplies the high-order 16 address bits. The debug module returns a not-ready response unless the received command is decoded as unimplemented, which is indicated by the illegal command encoding. If this occurs, the development system should retransmit the command.

NOTE:

Anot-ready response can be ignored except during a memory-referencing cycle. Otherwise, the debug module can accept a new serial transfer after 32 processor clock periods.

In cycle 3, the development system supplies the low-order 16 address bits. The debug module always returns a not-ready response.

29-22

MCF5282 User’s Manual

MOTOROLA

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Motorola MCF5282, MCF5281 user manual Command Sequence Diagrams