Background Debug Mode (BDM)

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.

29.5.2.1Receive Packet Format

The basic receive packet, Figure 29-13,consists of 16 data bits and 1 status bit

.

16

15

0

S

Data Field [15:0]

Figure 29-13. Receive BDM Packet

Table 29-15describes receive BDM packet fields.

 

 

 

Table 29-15. Receive BDM Packet Field Description

 

 

 

 

 

Bits

Name

 

 

Description

 

 

 

16

S

Status. Indicates the status of CPU-generated messages listed below. The not-ready response can be ignored

 

 

unless a memory-referencing cycle is in progress. Otherwise, the debug module can accept a new serial transfer

 

 

after 32 processor clock periods.

 

 

S

Data

Message

 

 

0

xxxx

Valid data transfer

 

 

0

0xFFFF

Status OK

 

 

1

0x0000

Not ready with response; come again

 

 

1

0x0001

Error—Terminated bus cycle; data invalid

 

 

1

0xFFFF

Illegal command

 

 

 

15–0

D

Data. Contains the message to be sent from the debug module to the development system. The response

 

 

message is always a single word, with the data field encoded as shown above.

 

 

 

 

 

29.5.2.2 Transmit Packet Format

The basic transmit packet, Figure 29-14,consists of 16 data bits and 1 control bit.

16

15

0

C

D

Figure 29-14. Transmit BDM Packet

Table 29-16describes transmit BDM packet fields.

 

 

Table 29-16. Transmit BDM Packet Field Description

 

 

 

Bits

Name

Description

 

 

 

16

C

Control. This bit is reserved. Command and data transfers initiated by the development system should clear C.

 

 

 

15–0

D

Data bits 15–0. Contains the data to be sent from the development system to the debug module.

 

 

 

MOTOROLA

Chapter 29. Debug Support

29-19

Page 691
Image 691
Motorola MCF5281, MCF5282 user manual Receive Packet Format, Transmit Packet Format, 15describes receive BDM packet fields